U.S. patent application number 17/255599 was filed with the patent office on 2021-08-26 for motion information encoding apparatus and encoding method, and motion information decoding apparatus and decoding method.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. The applicant listed for this patent is SAMSUNG ELECTRONICS CO., LTD. Invention is credited to Ki-ho CHOI, Na-rae CHOI, Woong-il CHOI, Seung-soo JEONG, Chan-yul KIM, Min-soo PARK, Min-woo PARK, Yin-ji PIAO, Anish TAMSE.
Application Number | 20210266561 17/255599 |
Document ID | / |
Family ID | 1000005614924 |
Filed Date | 2021-08-26 |
United States Patent
Application |
20210266561 |
Kind Code |
A1 |
JEONG; Seung-soo ; et
al. |
August 26, 2021 |
MOTION INFORMATION ENCODING APPARATUS AND ENCODING METHOD, AND
MOTION INFORMATION DECODING APPARATUS AND DECODING METHOD
Abstract
A method of decoding motion information includes determining a
coding factor value of a differential motion vector of a current
block, when adaptive encoding has been applied to the differential
motion vector, determining a first result value generated by
applying the adaptive encoding to the differential motion vector,
based on information included in the bitstream, obtaining the
differential motion vector by applying the determined coding factor
value to the first result value according to a certain operation,
and obtaining a motion vector of the current block, based on the
obtained differential motion vector and a prediction motion vector
of the current block.
Inventors: |
JEONG; Seung-soo; (Seoul,
KR) ; KIM; Chan-yul; (Seongnam-si, KR) ; PARK;
Min-soo; (Seoul, KR) ; PARK; Min-woo;
(Yongin-si, KR) ; CHOI; Ki-ho; (Seoul, KR)
; CHOI; Na-rae; (Seoul, KR) ; CHOI; Woong-il;
(Osan-si, KR) ; TAMSE; Anish; (Seoul, KR) ;
PIAO; Yin-ji; (Yongin-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG ELECTRONICS CO., LTD |
Suwon-si |
|
KR |
|
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
1000005614924 |
Appl. No.: |
17/255599 |
Filed: |
June 26, 2018 |
PCT Filed: |
June 26, 2018 |
PCT NO: |
PCT/KR2018/007213 |
371 Date: |
December 23, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N 19/115 20141101;
H04N 19/139 20141101; H04N 19/521 20141101; H04N 19/176
20141101 |
International
Class: |
H04N 19/139 20060101
H04N019/139; H04N 19/176 20060101 H04N019/176; H04N 19/513 20060101
H04N019/513; H04N 19/115 20060101 H04N019/115 |
Claims
1. A method of decoding motion information, the method comprising:
determining a coding factor value of a differential motion vector
of a current block, when adaptive encoding has been applied to the
differential motion vector; determining a first result value
generated by applying the adaptive encoding to the differential
motion vector, based on information included in a bitstream;
obtaining the differential motion vector by applying the determined
coding factor value to the first result value according to a
certain operation; and obtaining a motion vector of the current
block, based on the obtained differential motion vector and a
prediction motion vector of the current block.
2. The method of claim 1, wherein the determining of the first
result value comprises determining a second result value generated
by applying the adaptive encoding to the differential motion
vector, based on information included in the bitstream, and the
obtaining of the differential motion vector comprises obtaining the
differential motion vector by further applying the second result
value to the certain operation.
3. The method of claim 1, wherein the determining of the coding
factor value of the differential motion vector comprises: obtaining
factor value indicating information from the bitstream; and
determining the coding factor value, based on the obtained factor
value indicating information.
4. The method of claim 1, wherein the determining of the coding
factor value of the differential motion vector comprises
determining the coding factor value of the differential motion
vector, based on information related to at least one of the current
block, a pre-decoded block, a current slice including the current
block, a pre-decoded slice, a current picture including the current
block, and a pre-decoded picture.
5. The method of claim 1, further comprising, when the adaptive
encoding is not applied to the differential motion vector of the
current block, determining the differential motion vector of the
current block, based on information obtained from the
bitstream.
6. The method of claim 1, further comprising: determining a first
motion vector resolution of a first component of the motion vector
of the current block and a second motion vector resolution of a
second component of the motion vector of the current block;
adjusting a first component value and a second component value of
the prediction motion vector, based on results of comparisons
between a predetermined minimum motion vector resolution and each
of the first motion vector resolution and the second motion vector
resolution; and obtaining the motion vector of the current block,
based on the adjusted prediction motion vector and the differential
motion vector.
7. The method of claim 6, wherein the determining of the coding
factor value of the differential motion vector comprises
determining the coding factor value, based on the first motion
vector resolution and the second motion vector resolution.
8. The method of claim 6, wherein the adjusting of the first
component value and the second component value of the prediction
motion vector comprises adjusting the first component value of the
prediction motion vector when the first motion vector resolution is
greater than the minimum motion vector resolution, and adjusting
the second component value of the prediction motion vector when the
second motion vector resolution is greater than the minimum motion
vector resolution.
9. The method of claim 6, wherein the determining of the first
motion vector resolution and the second motion vector resolution
comprises determining the first motion vector resolution and the
second motion vector resolution, based on information representing
the first motion vector resolution, which is obtained from the
bitstream, and information representing the second motion vector
resolution, which is obtained from the bitstream.
10. The method of claim 6, wherein the determining of the first
motion vector resolution and the second motion vector resolution
comprises determining the first motion vector resolution and the
second motion vector resolution, based on a width and a height of
the current block.
11. The method of claim 10, wherein the determining of the first
motion vector resolution and the second motion vector resolution
comprises determining the first motion vector resolution and the
second motion vector resolution so that the first motion vector
resolution is greater than the second motion vector resolution,
when the width is larger than the height.
12. An image decoding apparatus comprising: an obtainer configured
to obtain a bitstream; and a prediction decoder configured to
determine a coding factor value of a differential motion vector of
a current block, when adaptive encoding has been applied to the
differential motion vector, determine a first result value
generated by applying the adaptive encoding to the differential
motion vector, based on information included in the bitstream,
obtain the differential motion vector by applying the determined
coding factor value to the first result value according to a
certain operation, and obtain a motion vector of the current block,
based on the obtained differential motion vector and a prediction
motion vector of the current block.
13. A method of encoding motion information, the method comprising:
obtaining a differential motion vector of a current block, based on
a motion vector of the current block and a prediction motion vector
of the current block; determining a coding factor value of the
differential motion vector, when adaptive encoding is applied to
the differential motion vector; obtaining a first result value of
the differential motion vector by applying the determined coding
factor value to the differential motion vector according to a
certain operation; and generating a bitstream, based on the first
result value of the differential motion vector.
14. The method of claim 13, further comprising obtaining a second
result value of the differential motion vector by applying the
determined coding factor value to the differential motion vector
according to the certain operation, and the generating of the
bitstream comprises generating the bitstream, based on the first
result value and the second result value of the differential motion
vector.
15. The method of claim 14, wherein the determining of the coding
factor value of the differential motion vector comprises, when each
of a plurality of factor value candidates is applied to the
differential motion vector, determining a factor value candidate
causing a smallest overall number of bits of a first result value
and a second result value of the differential motion vector and
factor value indication information representing a factor value
candidate, to be the coding factor value of the differential motion
vector of the current block.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to the field of image
encoding and image decoding. In particular, the present disclosure
relates to a method and apparatus for encoding motion information
of an image and a method and apparatus for decoding motion
information of an image.
BACKGROUND ART
[0002] In encoding and decoding of an image, one picture may be
split into blocks in order to encode an image, and each of the
blocks may be prediction-encoded via inter prediction or intra
prediction.
[0003] Inter prediction refers to a method of compressing an image
by removing temporal redundancy between pictures, a representative
example of which is motion estimation encoding. In the motion
estimation encoding, blocks of a current picture are predicted by
using at least one reference picture. A reference block most
similar to a current block may be searched for in a certain search
range by using a certain evaluation function. The current block is
predicted based on the reference block, and a residual block is
generated by subtracting a prediction block, generated as a result
of the prediction, from the current block and then encoded. Here,
to further accurately perform the prediction, interpolation is
performed on a search range of reference pictures so as to generate
pixels of sub pel units smaller than integer pel units, and inter
prediction may be performed based on the generated pixels of sub
pel units.
[0004] In a codec such as H.264advanced video coding (AVC) and high
efficiency video coding (HEVC), a motion vector of pre-encoded
blocks adjacent to a current block or blocks included in a
pre-encoded picture is used as a prediction motion vector of the
current block so as to predict a motion vector of the current
block. A differential motion vector that is a difference between
the motion vector of the current block and the prediction motion
vector is signaled to a decoder by using a certain method.
DESCRIPTION OF EMBODIMENTS
Technical Problem
[0005] Technical problems of an apparatus and method of encoding
motion information, and an apparatus and method of decoding motion
information, according to an embodiment, involve encoding the
differential motion vector of a current block at a low bitrate.
TECHNICAL SOLUTION TO PROBLEM
[0006] A method of decoding motion information, according to an
embodiment, includes determining a coding factor value of a
differential motion vector of a current block, when adaptive
encoding has been applied to the differential motion vector,
determining a first result value generated by applying the adaptive
encoding to the differential motion vector, based on information
included in the bitstream, obtaining the differential motion vector
by applying the determined coding factor value to the first result
value according to a certain operation, and obtaining a motion
vector of the current block, based on the obtained differential
motion vector and a prediction motion vector of the current
block.
Advantageous Effects of Disclosure
[0007] In an apparatus and method of encoding motion information,
and an apparatus and method of decoding motion information,
according to an embodiment, the differential motion vector of a
current block may be encoded at a low bitrate.
[0008] However, effects achievable by an apparatus and method of
encoding motion information and an apparatus and method of decoding
motion information are not limited to those mentioned above, and
other effects that not mentioned could be clearly understood by one
of ordinary skill in the art from the following description.
BRIEF DESCRIPTION OF DRAWINGS
[0009] A brief description of each drawing is provided to better
understand the drawings cited herein.
[0010] FIG. 1 is a block diagram of an image decoding apparatus
capable of decoding an image, based on at least one of block shape
information and split shape information, according to an
embodiment.
[0011] FIG. 2 is a block diagram of an image encoding apparatus
capable of encoding an image, based on at least one of block shape
information and split shape information, according to an
embodiment.
[0012] FIG. 3 illustrates a process of determining at least one
coding unit by splitting a current coding unit, according to an
embodiment.
[0013] FIG. 4 illustrates a process of determining at least one
coding unit by splitting a non-square coding unit, according to an
embodiment.
[0014] FIG. 5 illustrates a process of splitting a coding unit
based on at least one of block shape information and split shape
information, according to an embodiment.
[0015] FIG. 6 illustrates a method of determining a certain coding
unit from among an odd number of coding units, according to an
embodiment.
[0016] FIG. 7 illustrates an order of processing a plurality of
coding units when a current coding unit is split and the plurality
of coding units are determined, according to an embodiment.
[0017] FIG. 8 illustrates a process of determining that a current
coding unit is to be split into an odd number of coding units, when
the coding units are not processable in a certain order, according
to an embodiment.
[0018] FIG. 9 illustrates a process of determining at least one
coding unit by splitting a first coding unit, according to an
embodiment.
[0019] FIG. 10 illustrates that, when a second coding unit having a
non-square shape, which is determined by splitting a first coding
unit, satisfies a certain condition, a shape into which the second
coding unit is splittable is restricted, according to an
embodiment.
[0020] FIG. 11 illustrates a process of splitting a square coding
unit when split shape information is unable to indicate that the
square coding unit is split into four square coding units,
according to an embodiment.
[0021] FIG. 12 illustrates that a processing order between a
plurality of coding units may be changed depending on a process of
splitting a coding unit, according to an embodiment.
[0022] FIG. 13 illustrates a process of determining a depth of a
coding unit as a shape and size of the coding unit change, when the
coding unit is recursively split such that a plurality of coding
units are determined, according to an embodiment.
[0023] FIG. 14 illustrates depths that are determinable based on
shapes and sizes of coding units, and part indexes (PIDs) that are
for distinguishing the coding units, according to an
embodiment.
[0024] FIG. 15 illustrates that a plurality of coding units are
determined based on a plurality of certain data units included in a
picture, according to an embodiment.
[0025] FIG. 16 illustrates a processing block serving as a
criterion for determining a determination order of reference coding
units included in a picture, according to an embodiment.
[0026] FIG. 17 illustrates coding units that may be determined for
each picture when a combination of shapes into which a coding unit
is splittable is different for each picture, according to an
embodiment.
[0027] FIG. 18 illustrates various shapes of a coding unit that may
be determined based on split shape information representable in a
binary code, according to an embodiment.
[0028] FIG. 19 illustrates other shapes of a coding unit that may
be determined based on split shape information representable in a
binary code, according to an embodiment.
[0029] FIG. 20 is a block diagram of an image encoding and decoding
system that performs loop filtering.
[0030] FIG. 21 is a block diagram of an image decoding apparatus
according to an embodiment.
[0031] FIG. 22 is a table showing factor values corresponding to
factor value indicating indexes.
[0032] FIG. 23 is a diagram illustrating a motion vector, a
prediction motion vector, and a differential motion vector related
to a current block that is predicted bidirectionally.
[0033] FIG. 24 is a diagram illustrating a temporal and/or spatial
neighboring block temporally and/or spatially related to a current
block.
[0034] FIG. 25 is a table showing motion vector resolutions (MVRs)
corresponding to indexes.
[0035] FIG. 26 illustrates a syntax that obtains information about
an MVR from a bitstream.
[0036] FIG. 27 is a flowchart of a method of decoding motion
information, according to an embodiment.
[0037] FIG. 28 is a block diagram of an image encoding apparatus
according to an embodiment.
[0038] FIG. 29 is a flowchart of a method of encoding motion
information, according to an embodiment.
[0039] FIG. 30 illustrates positions of pixels that may be
indicated by motion vectors according to a 1/4 pixel unit MVR, a
1/2 pixel unit MVR, a 1 pixel unit MVR, and a 2 pixel unit MVR.
[0040] FIGS. 31 and 32 are views for explaining a prediction motion
vector adjusting method according to an embodiment.
BEST MODE
[0041] A method of decoding motion information, according to an
embodiment, includes determining a coding factor value of a
differential motion vector of a current block, when adaptive
encoding has been applied to the differential motion vector,
determining a first result value generated by applying the adaptive
encoding to the differential motion vector, based on information
included in the bitstream, obtaining the differential motion vector
by applying the determined coding factor value to the first result
value according to a certain operation, and obtaining a motion
vector of the current block, based on the obtained differential
motion vector and a prediction motion vector of the current
block.
[0042] The determining of the first result value may include
determining a second result value generated by applying the
adaptive encoding to the differential motion vector, based on
information included in the bitstream, and the determining of the
differential motion vector may include obtaining the differential
motion vector by further applying the second result value to the
certain operation.
[0043] The determining of the coding factor value of the
differential motion vector may include obtaining factor value
indicating information from the bitstream, and determining the
coding factor value, based on the obtained factor value indicating
information.
[0044] The determining of the coding factor value of the
differential motion vector may include determining the coding
factor value of the differential motion vector, based on
information related to at least one of the current block, a
pre-decoded block, a current slice including the current block, a
pre-decoded slice, a current picture including the current block,
and a pre-decoded picture.
[0045] The method may further include, when adaptive encoding is
not applied to the differential motion vector of the current block,
determining the differential motion vector of the current block,
based on information obtained from the bitstream.
[0046] The method may further include determining a first motion
vector resolution of a first component of the motion vector of the
current block and a second motion vector resolution of a second
component of the motion vector of the current block, adjusting a
first component value and a second component value of the
prediction motion vector, based on results of comparisons between a
predetermined minimum motion vector resolution and each of the
first motion vector resolution and the second motion vector
resolution, and obtaining the motion vector of the current block,
based on the adjusted prediction motion vector and the differential
motion vector.
[0047] The determining of the coding factor value of the
differential motion vector may include determining the coding
factor value, based on the first motion vector resolution and the
second motion vector resolution.
[0048] The adjusting of the first component value and the second
component value of the prediction motion vector may include
adjusting the first component value of the prediction motion vector
when the first motion vector resolution is greater than the minimum
motion vector resolution, and adjusting the second component value
of the prediction motion vector when the second motion vector
resolution is greater than the minimum motion vector
resolution.
[0049] The determining of the first motion vector resolution and
the second motion vector resolution may include determining the
first motion vector resolution and the second motion vector
resolution, based on information representing the first motion
vector resolution, which is obtained from the bitstream, and
information representing the second motion vector resolution, which
is obtained from the bitstream.
[0050] The determining of the first motion vector resolution and
the second motion vector resolution may include determining the
first motion vector resolution and the second motion vector
resolution, based on a width and a height of the current block.
[0051] The determining of the first motion vector resolution and
the second motion vector resolution may include determining the
first motion vector resolution and the second motion vector
resolution so that the first motion vector resolution is greater
than the second motion vector resolution, when the width is larger
than the height.
[0052] An image decoding apparatus includes an obtainer configured
to obtain a bitstream; and a prediction decoder configured to
determine a coding factor value of a differential motion vector of
a current block, when adaptive encoding has been applied to the
differential motion vector, determine a first result value
generated by applying the adaptive encoding to the differential
motion vector, based on information included in the bitstream,
obtain the differential motion vector by applying the determined
coding factor value to the first result value according to a
certain operation, and obtain a motion vector of the current block,
based on the obtained differential motion vector and a prediction
motion vector of the current block.
[0053] A method of encoding motion information includes obtaining a
differential motion vector of a current block, based on a motion
vector of the current block and a prediction motion vector of the
current block, determining a coding factor value of the
differential motion vector, when adaptive encoding is applied to
the differential motion vector, obtaining a first result value of
the differential motion vector by applying the determined coding
factor value to the differential motion vector according to a
certain operation, and generating a bitstream, based on the first
result value of the differential motion vector.
[0054] The method may further include obtaining a second result
value of the differential motion vector by applying the determined
coding factor value to the differential motion vector according to
the certain operation, and the generating of the bitstream may
include generating the bitstream, based on the first result value
and the second result value of the differential motion vector.
[0055] The determining of the coding factor value of the
differential motion vector may include, when each of a plurality of
factor value candidates is applied to the differential motion
vector, determining a factor value candidate causing a smallest
overall number of bits of a first result value and a second result
value of the differential motion vector and factor value indication
information representing a factor value candidate, to be the coding
factor value of the differential motion vector of the current
block.
MODE OF DISCLOSURE
[0056] As the disclosure allows for various changes and numerous
examples, particular embodiments will be illustrated in the
drawings and described in detail in the written description.
However, this is not intended to limit the disclosure to particular
modes of practice, and it will be understood that all changes,
equivalents, and substitutes that do not depart from the spirit and
technical scope of the disclosure are encompassed in the
disclosure.
[0057] In the description of embodiments, certain detailed
explanations of related art are omitted when it is deemed that they
may unnecessarily obscure the essence of the disclosure. Also,
numbers (for example, a first, a second, and the like) used in the
description of the specification are merely identifier codes for
distinguishing one element from another.
[0058] Also, in the present specification, it will be understood
that when elements are "connected" or "coupled" to each other, the
elements may be directly connected or coupled to each other, but
may alternatively be connected or coupled to each other with an
intervening element therebetween, unless specified otherwise.
[0059] In the present specification, regarding an element
represented as a "unit" or a "module", two or more elements may be
combined into one element or one element may be divided into two or
more elements according to subdivided functions. In addition, each
element described hereinafter may additionally perform some or all
of functions performed by another element, in addition to main
functions of itself, and some of the main functions of each element
may be performed entirely by another component.
[0060] Also, in the present specification, an `image` or a
`picture` may denote a still image of a video or a moving image,
i.e., the video itself.
[0061] Also, in the present specification, a `sample` denotes data
assigned to a sampling position of an image, i.e., data to be
processed. For example, pixel values of an image in a spatial
domain and transform coefficients on a transform region may be
samples. A unit including at least one such sample may be defined
as a block.
[0062] Also, in the present specification, a `current block` may
denote a block of a largest coding unit, coding unit, prediction
unit, or transform unit of a current image to be encoded or
decoded.
[0063] In addition, in the present specification, `motion vector
resolution (MVR)` refers to precision of a position of a pixel that
may be indicated by a motion vector determined through inter
prediction among the pixels included in a reference image (or an
interpolated reference image). When a motion vector resolution has
an N pixel unit (where N is a rational number), it means that a
motion vector may have precision of an N pixel unit. For example,
an MVR of a 1/4 pixel unit may mean that a motion vector may
indicate a pixel position of a 1/4 pixel unit (i.e., a subpixel
unit) in an interpolated reference image, and MVR of a 1 pixel unit
may mean that a motion vector may indicate a pixel position
corresponding to a 1 pixel unit (i.e., an integer pixel unit) in an
interpolated reference image.
[0064] In addition, in the present specification, a `candidate of
motion vector resolution` means one or more motion vector
resolutions that may be selected as the motion vector resolution of
a block.
[0065] Moreover, in this specification, the term `pixel unit` may
be replaced with terms such as pixel precision and pixel
accuracy.
[0066] Hereinafter, an image encoding method and apparatus and an
image decoding method and apparatus based on coding units and
transform units of a tree structure, according to an embodiment,
will be described with reference to FIGS. 1 through 20. An image
encoding apparatus 200 and an image decoding apparatus 100, which
will be described with reference to FIGS. 1 through 20, may
respectively include an image encoding apparatus 2800 and an image
decoding apparatus 2100, which will be described with reference to
FIGS. 21 through 32.
[0067] FIG. 1 is a block diagram of the image decoding apparatus
100 capable of decoding an image based on at least one of block
shape information and split shape information, according to an
embodiment.
[0068] Referring to FIG. 1, the image decoding apparatus 100 may
include a bitstream obtainer 110 for obtaining certain information
such as block shape information and split shape information from a
bitstream, and a decoder 120 for decoding an image by using the
obtained information. According to an embodiment, when the
bitstream obtainer 110 of the image decoding apparatus 100 obtains
at least one of block shape information and split shape
information, the decoder 120 of the image decoding apparatus 100
may determine at least one coding unit that splits an image based
on at least one of the block shape information and the split shape
information.
[0069] According to an embodiment, the decoder 120 of the image
decoding apparatus 100 may determine a shape of a coding unit,
based on the block shape information. For example, the block shape
information may include information indicating whether a coding
unit is a square or a non-square. The decoder 120 may determine a
shape of a coding unit by using the block shape information.
[0070] According to an embodiment, the decoder 120 may determine in
which shape a coding unit is to be split, based on the split shape
information. For example, the split shape information may represent
information about the shape of at least one coding unit included in
a coding unit.
[0071] According to an embodiment, the decoder 120 may determine
whether a coding unit is to be split or not to be split, according
to the split shape information. The split shape information may
include information on at least one coding unit included in a
coding unit, and, if the split shape information indicates that
only one coding unit is included in a coding unit or indicates that
the coding unit is not split, the decoder 120 may determine that
the coding unit including the split shape information is not split.
When the split shape information indicates that a coding unit is
split into a plurality of coding units, the decoder 120 may split
the coding unit into a plurality of coding units, based on the
split shape information.
[0072] According to an embodiment, the split shape information may
indicate how many coding units the coding unit is to be split into,
or in which direction the coding unit is to be split. For example,
the split shape information may indicate that the coding unit is
split in at least one of a vertical direction and a horizontal
direction or is not split.
[0073] FIG. 3 illustrates a process, performed by the image
decoding apparatus 100, of determining at least one coding unit by
splitting a current coding unit, according to an embodiment.
[0074] A block shape may include 4N.times.4N, 4N.times.2N,
2N.times.4N, 4N.times.N, or N.times.4N. Here, N may be a positive
integer. Block shape information is information indicating at least
one of a shape, direction, a ratio of width and height, or size of
a coding unit.
[0075] The shape of the coding unit may include a square and a
non-square. When the lengths of the width and height of the coding
unit are the same, the image decoding apparatus 100 may determine
the block shape information of the coding unit to be a square. The
image decoding apparatus 100 may determine the shape of the coding
unit to be a non-square.
[0076] When the lengths of the width and height of the coding unit
are different (4N.times.2N, 2N.times.4N, 4N.times.N, or
N.times.4N), the image decoding apparatus 100 may determine the
block shape information of the coding unit to be a non-square. When
the shape of the coding unit is non-square, the image decoding
apparatus 100 may determine the ratio of the width and height among
the block shape information of the coding unit to be at least one
of 1:2, 2:1, 1:4, 4:1, 1:8, or 8:1. Also, the image decoding
apparatus 100 may determine whether the coding unit is in a
horizontal direction or a vertical direction, based on the length
of the width of the coding unit and the length of the height of the
coding unit. Also, the image decoding apparatus 100 may determine
the size of the coding unit, based on at least one of the length of
the width of the coding unit, the length of the height of the
coding unit, or the area of the coding unit.
[0077] According to an embodiment, the image decoding apparatus 100
may determine the shape of the coding unit by using the block shape
information, and may determine a splitting method of the coding
unit by using information about a split shape mode. In other words,
a coding unit splitting method indicated by the information about
the split shape mode may be determined based on a block shape
indicated by the block shape information used by the image decoding
apparatus 100.
[0078] The image decoding apparatus 100 may obtain the information
about the split shape mode from a bitstream. However, embodiments
are not limited thereto, and the image decoding apparatus 100 and
the image encoding apparatus 200 may obtain information about a
pre-agreed split shape mode, based on the block shape information.
The image decoding apparatus 100 may obtain the information about
the pre-agreed split shape mode with respect to a largest coding
unit or a smallest coding unit. For example, the image decoding
apparatus 100 may determine the size of the largest coding unit to
be 256.times.256. The image decoding apparatus 100 may determine
the information about the pre-agreed split shape mode to be a quad
split. The quad split is a split shape mode in which the width and
the height of the coding unit are both bisected. The image decoding
apparatus 100 may obtain a coding unit of a 128.times.128 size from
the largest coding unit of a 256.times.256 size, based on the
information about the split shape mode. Also, the image decoding
apparatus 100 may determine the size of the smallest coding unit to
be 4.times.4. The image decoding apparatus 100 may obtain
information about a split shape mode indicating "not to perform
splitting" with respect to the smallest coding unit.
[0079] According to an embodiment, the image decoding apparatus 100
may use the block shape information indicating that the current
coding unit has a square shape. For example, the image decoding
apparatus 100 may determine whether not to split a square coding
unit, whether to vertically split the square coding unit, whether
to horizontally split the square coding unit, or whether to split
the square coding unit into four coding units, based on the
information about the split shape mode. Referring to FIG. 3, when
the block shape information of a current coding unit 300 indicates
a square shape, the decoder 120 may determine that a coding unit
310a having the same size as the current coding unit 300 is not
split, based on the information about the split shape mode
indicating not to perform splitting, or may determine coding units
310b, 310c, 310d, etc. split based on the information about the
split shape mode indicating a certain splitting method.
[0080] Referring to FIG. 3, according to an embodiment, the image
decoding apparatus 100 may determine two coding units 310b obtained
by splitting the current coding unit 300 in a vertical direction,
based on the information about the split shape mode indicating to
perform splitting in a vertical direction. The image decoding
apparatus 100 may determine two coding units 310c obtained by
splitting the current coding unit 300 in a horizontal direction,
based on the information about the split shape mode indicating to
perform splitting in a horizontal direction. The image decoding
apparatus 100 may determine four coding units 310d obtained by
splitting the current coding unit 300 in vertical and horizontal
directions, based on the information about the split shape mode
indicating to perform splitting in vertical and horizontal
directions. However, splitting methods of the square coding unit
are not limited to the above-described methods, and the information
about the split shape mode may indicate various methods. Certain
splitting methods of splitting the square coding unit will be
described in detail below in relation to various embodiments.
[0081] FIG. 4 illustrates a process, performed by the image
decoding apparatus 100, of determining at least one coding unit by
splitting a non-square coding unit, according to an embodiment.
[0082] According to an embodiment, the image decoding apparatus 100
may use block shape information indicating that a current coding
unit has a non-square shape. The image decoding apparatus 100 may
determine whether not to split the non-square current coding unit
or whether to split the non-square current coding unit by using a
certain splitting method, based on the information about the split
shape mode. Referring to FIG. 4, when the block shape information
of a current coding unit 400 or 450 indicates a non-square shape,
the image decoding apparatus 100 may determine that a coding unit
410 or 460 having the same size as the current coding unit 400 or
450 is not split, based on the information about the split shape
mode indicating not to perform splitting, or determine coding units
420a and 420b, 430a to 430c, 470a and 470b, or 480a to 480c split
based on the information about the split shape mode indicating a
certain splitting method. Certain splitting methods of splitting a
non-square coding unit will be described in detail below in
relation to various embodiments.
[0083] According to an embodiment, the image decoding apparatus 100
may determine a splitting method of a coding unit by using the
information about the split shape mode and, in this case, the
information about the split shape mode may indicate the number of
one or more coding units generated by splitting a coding unit.
Referring to FIG. 4, when the information about the split shape
mode indicates to split the current coding unit 400 or 450 into two
coding units, the image decoding apparatus 100 may determine two
coding units 420a and 420b, or 470a and 470b included in the
current coding unit 400 or 450, by splitting the current coding
unit 400 or 450 based on the information about the split shape
mode.
[0084] According to an embodiment, when the image decoding
apparatus 100 splits the non-square current coding unit 400 or 450
based on the information about the split shape mode, the image
decoding apparatus 100 may consider the location of a long side of
the non-square current coding unit 400 or 450 to split a current
coding unit. For example, the image decoding apparatus 100 may
determine a plurality of coding units by splitting a long side of
the current coding unit 400 or 450, in consideration of the shape
of the current coding unit 400 or 450.
[0085] According to an embodiment, when the information about the
split shape mode indicates to split (ternary-split) a coding unit
into an odd number of blocks, the image decoding apparatus 100 may
determine an odd number of coding units included in the current
coding unit 400 or 450. For example, when the information about the
split shape mode indicates to split the current coding unit 400 or
450 into three coding units, the image decoding apparatus 100 may
split the current coding unit 400 or 450 into three coding units
430a, 430b, and 430c, or 480a, 480b, and 480c.
[0086] According to an embodiment, a ratio of the width and height
of the current coding unit 400 or 450 may be 4:1 or 1:4. When the
ratio of the width and height is 4:1, the block shape information
may be a horizontal direction because the length of the width is
longer than the length of the height. When the ratio of the width
and height is 1:4, the block shape information may be a vertical
direction because the length of the width is shorter than the
length of the height. The image decoding apparatus 100 may
determine to split a current coding unit into the odd number of
blocks, based on the information about the split shape mode. Also,
the image decoding apparatus 100 may determine a split direction of
the current coding unit 400 or 450, based on the block shape
information of the current coding unit 400 or 450. For example,
when the current coding unit 400 is in the vertical direction, the
image decoding apparatus 100 may determine the coding units 430a to
430c by splitting the current coding unit 400 in the horizontal
direction. Also, when the current coding unit 450 is in the
horizontal direction, the image decoding apparatus 100 may
determine the coding units 480a to 480c by splitting the current
coding unit 450 in the vertical direction.
[0087] According to an embodiment, the image decoding apparatus 100
may determine the odd number of coding units included in the
current coding unit 400 or 450, and not all the determined coding
units may have the same size. For example, a certain coding unit
430b or 480b from among the determined odd number of coding units
430a, 430b, and 430c, or 480a, 480b, and 480c may have a size
different from the sizes of the other coding units 430a and 430c,
or 480a and 480c. In other words, coding units which may be
determined by splitting the current coding unit 400 or 450 may have
multiple sizes and, in some cases, all of the odd number of coding
units 430a, 430b, and 430c, or 480a, 480b, and 480c may have
different sizes.
[0088] According to an embodiment, when the information about the
split shape mode indicates to split a coding unit into the odd
number of blocks, the image decoding apparatus 100 may determine
the odd number of coding units included in the current coding unit
400 or 450, and in addition, may put a certain restriction on at
least one coding unit from among the odd number of coding units
generated by splitting the current coding unit 400 or 450.
Referring to FIG. 4, the image decoding apparatus 100 may set a
decoding process regarding the coding unit 430b or 480b located at
the center among the three coding units 430a, 430b, and 430c or
480a, 480b, and 480c generated by splitting the current coding unit
400 or 450 to be different from that of the other coding units 430a
and 430c, or 480a or 480c. For example, the image decoding
apparatus 100 may restrict the coding unit 430b or 480b at the
center location to be no longer split or to be split only a certain
number of times, unlike the other coding units 430a and 430c, or
480a and 480c.
[0089] FIG. 5 illustrates a process, performed by the image
decoding apparatus 100, of splitting a coding unit based on at
least one of block shape information and information about a split
shape mode, according to an embodiment.
[0090] According to an embodiment, the image decoding apparatus 100
may determine to split or not to split a square first coding unit
500 into coding units, based on at least one of the block shape
information and the information about the split shape mode.
According to an embodiment, when the information about the split
shape mode indicates to split the first coding unit 500 in a
horizontal direction, the image decoding apparatus 100 may
determine a second coding unit 510 by splitting the first coding
unit 500 in a horizontal direction. A first coding unit, a second
coding unit, and a third coding unit used according to an
embodiment are terms used to understand a relation before and after
splitting a coding unit. For example, a second coding unit may be
determined by splitting a first coding unit, and a third coding
unit may be determined by splitting the second coding unit. It will
now be understood that a relationship between the first coding
unit, the second coding unit, and the third coding unit follows the
above descriptions.
[0091] According to an embodiment, the image decoding apparatus 100
may determine to split or not to split the determined second coding
unit 510 into coding units, based on at least one of the block
shape information and the information about the split shape mode.
Referring to FIG. 5, the image decoding apparatus 100 may or may
not split the non-square second coding unit 510, which is
determined by splitting the first coding unit 500, into one or more
third coding units 520a, or 520b, 520c, and 520d based on at least
one of the block shape information and the information about the
split shape mode. The image decoding apparatus 100 may obtain at
least one of the block shape information and the information about
the split shape mode, and may obtain a plurality of various-shaped
second coding units (e.g., 510) by splitting the first coding unit
500, based on the obtained at least one of the block shape
information and the information about the split shape mode, and the
second coding unit 510 may be split by using a splitting method of
the first coding unit 500 based on at least one of the block shape
information and the information about the split shape mode.
According to an embodiment, when the first coding unit 500 is split
into the second coding units 510 based on at least one of the block
shape information and the information about the split shape mode of
the first coding unit 500, the second coding unit 510 may also be
split into the third coding units 520a, or 520b, 520c, and 520d
based on at least one of the block shape information and the
information about the split shape mode of the second coding unit
510. In other words, a coding unit may be recursively split based
on at least one of the block shape information and the information
about the split shape mode of each coding unit. Therefore, a square
coding unit may be determined by splitting a non-square coding
unit, and a non-square coding unit may be determined by recursively
splitting the square coding unit.
[0092] Referring to FIG. 5, a certain coding unit from among the
odd number of third coding units 520b, 520c, and 520d determined by
splitting the non-square second coding unit 510 (e.g., a coding
unit at a center location or a non-square coding unit) may be
recursively split. According to an embodiment, the non-square third
coding unit 520b from among the odd number of third coding units
520b, 520c, and 520d may be split in a horizontal direction into a
plurality of fourth coding units. A non-square fourth coding unit
530b or 530d from among a plurality of fourth coding units 530a,
530b, 530c, and 530d may be split into a plurality of coding units
again. For example, the non-square fourth coding unit 530b or 530d
may be split into the odd number of coding units again. A method
that may be used to recursively split a coding unit will be
described below in relation to various embodiments.
[0093] According to an embodiment, the image decoding apparatus 100
may split each of the third coding units 520a, or 520b, 520c, and
520d into coding units, based on at least one of the block shape
information and the information about the split shape mode. In
addition, the image decoding apparatus 100 may determine to not to
split the second coding unit 510, based on at least one of the
block shape information and the information about the split shape
mode. According to an embodiment, the image decoding apparatus 100
may split the non-square second coding unit 510 into the odd number
of third coding units 520b, 520c, and 520d. The image decoding
apparatus 100 may put a certain restriction on a certain third
coding unit from among the odd number of third coding units 520b,
520c, and 520d. For example, the image decoding apparatus 100 may
restrict the third coding unit 520c at a center location from among
the odd number of third coding units 520b, 520c, and 520d to be no
longer split or to be split a settable number of times.
[0094] Referring to FIG. 5, the image decoding apparatus 100 may
restrict the third coding unit 520c, which is at the center
location from among the odd number of third coding units 520b,
520c, and 520d included in the non-square second coding unit 510,
to be no longer split, to be split by using a certain splitting
method (e.g., split into only four coding units or split by using a
splitting method of the second coding unit 510), or to be split
only a certain number of times (e.g., split only n times (where
n>0)). However, the restrictions on the third coding unit 520c
at the center location are merely simple embodiments and thus are
not limited to the above-described examples, and may include
various restrictions for decoding the third coding unit 520c at the
center location differently from the other third coding units 520b
and 520d.
[0095] According to an embodiment, the image decoding apparatus 100
may obtain at least one of the block shape information and the
information about the split shape mode, which are used to split a
current coding unit, from a certain location in the current coding
unit.
[0096] FIG. 6 illustrates a method, performed by the image decoding
apparatus 100, of determining a certain coding unit from among an
odd number of coding units, according to an embodiment.
[0097] Referring to FIG. 6, at least one of block shape information
and information about a split shape mode of a current coding unit
600 or 650 may be obtained from a sample at a certain location
(e.g., a sample 640 or 690 at a center location) from among a
plurality of samples included in the current coding unit 600 or
650. However, the certain location in the current coding unit 600,
from which at least one of the block shape information and the
information about the split shape mode may be obtained, is not
limited to the center location in FIG. 6, and may include various
locations included in the current coding unit 600 (e.g., top,
bottom, left, right, upper left, lower left, upper right, and lower
right locations). The image decoding apparatus 100 may obtain at
least one of the block shape information and the information about
the split shape mode from the certain location and may determine to
split or not to split the current coding unit into various-shaped
and various-sized coding units.
[0098] According to an embodiment, when the current coding unit is
split into a certain number of coding units, the image decoding
apparatus 100 may select one of the coding units. Various methods
may be used to select one of a plurality of coding units, as will
be described below in relation to various embodiments.
[0099] According to an embodiment, the image decoding apparatus 100
may split the current coding unit into a plurality of coding units,
and may determine a coding unit at a certain location.
[0100] According to an embodiment, the image decoding apparatus 100
may use information indicating respective locations of the odd
number of coding units, to determine a coding unit at a center
location from among the odd number of coding units. Referring to
FIG. 6, the image decoding apparatus 100 may determine an odd
number of coding units 620a, 620b, and 620c or an odd number of
coding units 660a, 660b, and 660c by splitting the current coding
unit 600 or the current coding unit 650, respectively. The image
decoding apparatus 100 may determine the middle coding unit 620b or
the middle coding unit 660b by using information about the
locations of the odd number of coding units 620a, 620b, and 620c or
the odd number of coding units 660a, 660b, and 660c. For example,
the image decoding apparatus 100 may determine the coding unit 620b
at the center location by determining the respective locations of
the coding units 620a, 620b, and 620c based on information
indicating locations of certain samples included in the coding
units 620a, 620b, and 620c. In detail, the image decoding apparatus
100 may determine the coding unit 620b at the center location by
determining the respective locations of the coding units 620a,
620b, and 620c based on information indicating respective locations
of upper left samples 630a, 630b, and 630c of the coding units
620a, 620b, and 620c.
[0101] According to an embodiment, the information indicating the
respective locations of the upper left samples 630a, 630b, and
630c, which are included in the coding units 620a, 620b, and 620c,
respectively, may include information about respective locations or
coordinates of the coding units 620a, 620b, and 620c in a picture.
According to an embodiment, the information indicating the
respective locations of the upper left samples 630a, 630b, and
630c, which are included in the coding units 620a, 620b, and 620c,
respectively, may include information indicating respective widths
or heights of the coding units 620a, 620b, and 620c included in the
current coding unit 600, and the widths or heights may correspond
to information indicating differences between the respective
coordinates of the coding units 620a, 620b, and 620c in the
picture. In other words, the image decoding apparatus 100 may
determine the coding unit 620b at the center location by directly
using the information about the locations or coordinates of the
coding units 620a, 620b, and 620c in the picture, or by using the
information about the widths or heights of the coding units, which
correspond to the difference values between the coordinates.
[0102] According to an embodiment, information indicating the
location of the upper left sample 630a of the upper coding unit
620a may include coordinates (xa, ya), information indicating the
location of the upper left sample 630b of the middle coding unit
620b may include coordinates (xb, yb), and information indicating
the location of the upper left sample 630c of the lower coding unit
620c may include coordinates (xc, yc). The image decoding apparatus
100 may determine the middle coding unit 620b by using the
coordinates of the upper left samples 630a, 630b, and 630c which
are included in the coding units 620a, 620b, and 620c,
respectively. For example, when the coordinates of the upper left
samples 630a, 630b, and 630c are sorted in an ascending or
descending order, the coding unit 620b including the coordinates
(xb, yb) of the sample 630b at the center location may be
determined as a coding unit at a center location from among the
coding units 620a, 620b, and 620c determined by splitting the
current coding unit 600. However, the coordinates indicating the
locations of the upper left samples 630a, 630b, and 630c may
include coordinates indicating absolute locations in the picture,
or may use coordinates (dxb, dyb) that is information indicating a
relative location of the upper left sample 630b of the middle
coding unit 620b and coordinates (dxc, dyc) that is information
indicating a relative location of the upper left sample 630c of the
lower coding unit 620c with reference to the location of the upper
left sample 630a of the upper coding unit 620a. A method of
determining a coding unit at a certain location by using
coordinates of a sample included in the coding unit, as information
indicating a location of the sample, is not limited to the
above-described method, and may include various arithmetic methods
capable of using the coordinates of the sample.
[0103] According to an embodiment, the image decoding apparatus 100
may split the current coding unit 600 into a plurality of coding
units 620a, 620b, and 620c, and may select one of the coding units
620a, 620b, and 620c based on a certain criterion. For example, the
image decoding apparatus 100 may select the coding unit 620b, which
has a size different from that of the others, from among the coding
units 620a, 620b, and 620c.
[0104] According to an embodiment, the image decoding apparatus 100
may determine the width or height of each of the coding units 620a,
620b, and 620c by using the coordinates (xa, ya) that is the
information indicating the location of the upper left sample 630a
of the upper coding unit 620a, the coordinates (xb, yb) that is the
information indicating the location of the upper left sample 630b
of the middle coding unit 620b, and the coordinates (xc, yc) that
is the information indicating the location of the upper left sample
630c of the lower coding unit 620c. The image decoding apparatus
100 may determine the respective sizes of the coding units 620a,
620b, and 620c by using the coordinates (xa, ya), (xb, yb), and
(xc, yc) indicating the respective locations of the coding units
620a, 620b, and 620c. According to an embodiment, the image
decoding apparatus 100 may determine the width of the upper coding
unit 620a to be the width of the current coding unit 600. The image
decoding apparatus 100 may determine the height of the upper coding
unit 620a to be yb-ya. According to an embodiment, the image
decoding apparatus 100 may determine the width of the middle coding
unit 620b to be the width of the current coding unit 600. The image
decoding apparatus 100 may determine the height of the middle
coding unit 620b to be yc-yb. According to an embodiment, the image
decoding apparatus 100 may determine the width or height of the
lower coding unit 620c by using the width or height of the current
coding unit 600 and the widths or heights of the upper and middle
coding units 620a and 620b. The image decoding apparatus 100 may
determine a coding unit having a different size from that of the
others, based on the determined widths and heights of the coding
units 620a to 620c. Referring to FIG. 6, the image decoding
apparatus 100 may determine the middle coding unit 620b, which has
a size different from the size of the upper and lower coding units
620a and 620c, as the coding unit at the certain location. However,
the above-described method, performed by the image decoding
apparatus 100, of determining a coding unit having a size different
from the size of the other coding units merely corresponds to an
example of determining a coding unit at a certain location by using
the sizes of coding units, which are determined based on the
coordinates of samples, and thus various methods of determining a
coding unit at a certain location by comparing the sizes of coding
units, which are determined based on coordinates of certain
samples, may be used.
[0105] The image decoding apparatus 100 may determine the width or
height of each of the coding units 660a, 660b, and 660c by using
the coordinates (xd, yd) that are information indicating the
location of a upper left sample 670a of the left coding unit 660a,
the coordinates (xe, ye) that are information indicating the
location of a upper left sample 670b of the middle coding unit
660b, and the coordinates (xf, yf) that are information indicating
a location of the upper left sample 670c of the right coding unit
660c. The image decoding apparatus 100 may determine the respective
sizes of the coding units 660a, 660b, and 660c by using the
coordinates (xd, yd), (xe, ye), and (xf, yf) indicating the
respective locations of the coding units 660a, 660b, and 660c.
[0106] According to an embodiment, the image decoding apparatus 100
may determine the width of the left coding unit 660a to be xe-xd.
The image decoding apparatus 100 may determine the height of the
left coding unit 660a to be the height of the current coding unit
650. According to an embodiment, the image decoding apparatus 100
may determine the width of the middle coding unit 660b to be xf-xe.
The image decoding apparatus 100 may determine the height of the
middle coding unit 660b to be the height of the current coding unit
650. According to an embodiment, the image decoding apparatus 100
may determine the width or height of the right coding unit 660c by
using the width or height of the current coding unit 650 and the
widths or heights of the left and middle coding units 660a and
660b. The image decoding apparatus 100 may determine a coding unit
having a different size from that of the others, based on the
determined widths and heights of the coding units 660a to 660c.
Referring to FIG. 6, the image decoding apparatus 100 may determine
the middle coding unit 660b, which has a size different from the
sizes of the left and right coding units 660a and 660c, as the
coding unit at the certain location. However, the above-described
method, performed by the image decoding apparatus 100, of
determining a coding unit having a size different from the size of
the other coding units merely corresponds to an example of
determining a coding unit at a certain location by using the sizes
of coding units, which are determined based on the coordinates of
samples, and thus various methods of determining a coding unit at a
certain location by comparing the sizes of coding units, which are
determined based on coordinates of certain samples, may be
used.
[0107] However, locations of samples considered to determine
locations of coding units are not limited to the above-described
upper left locations, and information about locations of arbitrary
samples included in the coding units may be used.
[0108] According to an embodiment, the image decoding apparatus 100
may select a coding unit at a certain location from among an odd
number of coding units determined by splitting the current coding
unit, considering the shape of the current coding unit. For
example, when the current coding unit has a non-square shape, a
width of which is longer than a height, the image decoding
apparatus 100 may determine the coding unit at the certain location
in a horizontal direction. That is, the image decoding apparatus
100 may determine one of coding units at different locations in a
horizontal direction and put a restriction on the coding unit. When
the current coding unit has a non-square shape, a height of which
is longer than a width, the image decoding apparatus 100 may
determine the coding unit at the certain location in a vertical
direction. In other words, the image decoding apparatus 100 may
determine one of coding units at different locations in a vertical
direction and may put a restriction on the coding unit.
[0109] According to an embodiment, the image decoding apparatus 100
may use information indicating respective locations of an even
number of coding units, to determine the coding unit at the certain
location from among the even number of coding units. The image
decoding apparatus 100 may determine an even number of coding units
by splitting (binary-splitting) the current coding unit, and may
determine the coding unit at the certain location by using the
information about the locations of the even number of coding units.
An operation related thereto may correspond to the operation of
determining a coding unit at a certain location (e.g., a center
location) from among an odd number of coding units, which has been
described in detail above in relation to FIG. 6, and thus detailed
descriptions thereof are not provided here.
[0110] According to an embodiment, when a non-square current coding
unit is split into a plurality of coding units, certain information
about a coding unit at a certain location may be used in a
splitting operation to determine the coding unit at the certain
location from among the plurality of coding units. For example, the
image decoding apparatus 100 may use at least one of block shape
information and information about a split shape mode, which is
stored in a sample included in a middle coding unit, in a splitting
operation to determine a coding unit at a center location from
among the plurality of coding units determined by splitting the
current coding unit.
[0111] Referring to FIG. 6, the image decoding apparatus 100 may
split the current coding unit 600 into the plurality of coding
units 620a, 620b, and 620c based on at least one of the block shape
information and the information about the split shape mode, and may
determine the coding unit 620b at a center location from among the
plurality of the coding units 620a, 620b, and 620c. Furthermore,
the image decoding apparatus 100 may determine the coding unit 620b
at the center location, in consideration of a location from which
at least one of the block shape information and the information
about the split shape mode is obtained. In other words, at least
one of the block shape information and the information about the
split shape mode of the current coding unit 600 may be obtained
from the sample 640 at a center location of the current coding unit
600, and, when the current coding unit 600 is split into the
plurality of coding units 620a, 620b, and 620c based on at least
one of the block shape information and the information about the
split shape mode, the coding unit 620b including the sample 640 may
be determined as the coding unit at the center location. However,
information used to determine the coding unit at the center
location is not limited to at least one of the block shape
information and the information about the split shape mode, and
various types of information may be used to determine the coding
unit at the center location.
[0112] According to an embodiment, certain information for
identifying the coding unit at the certain location may be obtained
from a certain sample included in a coding unit to be determined.
Referring to FIG. 6, the image decoding apparatus 100 may use at
least one of the block shape information and the information about
the split shape mode, which is obtained from a sample at a certain
location in the current coding unit 600 (e.g., a sample at a center
location of the current coding unit 600) to determine a coding unit
at a certain location from among the plurality of the coding units
620a, 620b, and 620c determined by splitting the current coding
unit 600 (e.g., a coding unit at a center location from among a
plurality of split coding units). In other words, the image
decoding apparatus 100 may determine the sample at the certain
location by considering a block shape of the current coding unit
600, determine the coding unit 620b including a sample, from which
certain information (e.g., at least one of the block shape
information and the information about the split shape mode) may be
obtained, from among the plurality of coding units 620a, 620b, and
620c determined by splitting the current coding unit 600, and may
put a certain restriction on the coding unit 620b. Referring to
FIG. 6, according to an embodiment, the image decoding apparatus
100 may determine the sample 640 at the center location of the
current coding unit 600 as the sample from which the certain
information may be obtained, and may put a certain restriction on
the coding unit 620b including the sample 640, in a decoding
operation. However, the location of the sample from which the
certain information may be obtained is not limited to the
above-described location, and may include arbitrary locations of
samples included in the coding unit 620b to be determined for a
restriction.
[0113] According to an embodiment, the location of the sample from
which the certain information may be obtained may be determined
based on the shape of the current coding unit 600. According to an
embodiment, the block shape information may indicate whether the
current coding unit has a square or non-square shape, and the
location of the sample from which the certain information may be
obtained may be determined based on the shape. For example, the
image decoding apparatus 100 may determine a sample located on a
boundary for splitting at least one of a width and height of the
current coding unit in half, as the sample from which the certain
information may be obtained, by using at least one of information
about the width of the current coding unit and information about
the height of the current coding unit. As another example, when the
block shape information of the current coding unit indicates a
non-square shape, the image decoding apparatus 100 may determine
one of samples adjacent to a boundary for splitting a long side of
the current coding unit in half, as the sample from which the
certain information may be obtained.
[0114] According to an embodiment, when the current coding unit is
split into a plurality of coding units, the image decoding
apparatus 100 may use at least one of the block shape information
and the information about the split shape mode to determine a
coding unit at a certain location from among the plurality of
coding units. According to an embodiment, the image decoding
apparatus 100 may obtain at least one of the block shape
information and the information about the split shape mode from a
sample at a certain location in a coding unit, and split the
plurality of coding units, which are generated by splitting the
current coding unit, by using at least one of the block shape
information and the information about the split shape mode, which
is obtained from the sample of the certain location in each of the
plurality of coding units. In other words, a coding unit may be
recursively split based on at least one of the block shape
information and the information about the split shape mode, which
is obtained from the sample at the certain location included in
each coding unit. An operation of recursively splitting a coding
unit has been described above in relation to FIG. 5, and thus
detailed descriptions thereof will not be provided here.
[0115] According to an embodiment, the image decoding apparatus 100
may determine one or more coding units by splitting the current
coding unit, and may determine an order of decoding the one or more
coding units, based on a certain block (e.g., the current coding
unit).
[0116] FIG. 7 illustrates an order of processing a plurality of
coding units when the image decoding apparatus 100 determines the
plurality of coding units by splitting a current coding unit,
according to an embodiment.
[0117] According to an embodiment, the image decoding apparatus 100
may determine second coding units 710a and 710b by splitting a
first coding unit 700 in a vertical direction, determine second
coding units 730a and 730b by splitting the first coding unit 700
in a horizontal direction, or determine second coding units 750a to
750d by splitting the first coding unit 700 in vertical and
horizontal directions, based on block shape information and
information about a split shape mode.
[0118] Referring to FIG. 7, the image decoding apparatus 100 may
determine to process the second coding units 710a and 710b
determined by splitting the first coding unit 700 in a vertical
direction, in a horizontal direction order 710c. The image decoding
apparatus 100 may determine to process the second coding units 730a
and 730b determined by splitting the first coding unit 700 in a
horizontal direction, in a vertical direction order 730c. The image
decoding apparatus 100 may determine to process the second coding
units 750a to 750d determined by splitting the first coding unit
700 in vertical and horizontal directions, in a certain order for
processing coding units in a row and then processing coding units
in a next row (e.g., in a raster scan order or Z-scan order
750e).
[0119] According to an embodiment, the image decoding apparatus 100
may recursively split coding units. Referring to FIG. 7, the image
decoding apparatus 100 may determine the plurality of coding units
710a and 710b, 730a and 730b, or 750a to 750d by splitting the
first coding unit 700, and recursively split each of the determined
plurality of coding units 710b, 730a and 730b, or 750a to 750d. A
splitting method of the plurality of coding units 710b, 730a and
730b, or 750a to 750d may correspond to a splitting method of the
first coding unit 700. Accordingly, each of the plurality of coding
units 710b, 730a and 730b, or 750a to 750d may be independently
split into a plurality of coding units. Referring to FIG. 7, the
image decoding apparatus 100 may determine the second coding units
710a and 710b by splitting the first coding unit 700 in a vertical
direction, and may determine to independently split or not to split
each of the second coding units 710a and 710b.
[0120] According to an embodiment, the image decoding apparatus 100
may determine third coding units 720a and 720b by splitting the
left second coding unit 710a in a horizontal direction, and may not
split the right second coding unit 710b.
[0121] According to an embodiment, a processing order of coding
units may be determined based on an operation of splitting a coding
unit. In other words, a processing order of split coding units may
be determined based on a processing order of coding units
immediately before being split. The image decoding apparatus 100
may determine a processing order of the third coding units 720a and
720b determined by splitting the left second coding unit 710a,
independently of the right second coding unit 710b. Because the
third coding units 720a and 720b are determined by splitting the
left second coding unit 710a in a horizontal direction, the third
coding units 720a and 720b may be processed in a vertical direction
order 720c. Because the left and right second coding units 710a and
710b are processed in the horizontal direction order 710c, the
right second coding unit 710b may be processed after the third
coding units 720a and 720b included in the left second coding unit
710a are processed in the vertical direction order 720c. An
operation of determining a processing order of coding units based
on a coding unit before being split is not limited to the
above-described example, and various methods may be used to
independently process coding units, which are split and determined
to various shapes, in a certain order.
[0122] FIG. 8 illustrates a process, performed by the image
decoding apparatus 100, of determining that a current coding unit
is to be split into an odd number of coding units, when the coding
units are not processable in a certain order, according to an
embodiment.
[0123] According to an embodiment, the image decoding apparatus 100
may determine whether the current coding unit is split into an odd
number of coding units, based on obtained block shape information
and obtained information about a split shape mode. Referring to
FIG. 8, a square first coding unit 800 may be split into non-square
second coding units 810a and 810b, and the second coding units 810a
and 810b may be independently split into third coding units 820a
and 820b, and 820c to 820e. According to an embodiment, the image
decoding apparatus 100 may determine the plurality of third coding
units 820a and 820b by splitting the left second coding unit 810a
in a horizontal direction, and may split the right second coding
unit 810b into the odd number of third coding units 820c to
820e.
[0124] According to an embodiment, the image decoding apparatus 100
may determine whether any coding unit is split into an odd number
of coding units, by determining whether the third coding units 820a
and 820b, and 820c to 820e are processable in a certain order.
Referring to FIG. 8, the image decoding apparatus 100 may determine
the third coding units 820a and 820b, and 820c to 820e by
recursively splitting the first coding unit 800. The image decoding
apparatus 100 may determine whether any of the first coding unit
800, the second coding units 810a and 810b, and the third coding
units 820a and 820b, and 820c to 820e are split into an odd number
of coding units, based on at least one of the block shape
information and the information about the split shape mode. For
example, the right second coding unit 810b among the second coding
units 810a and 810b may be split into an odd number of third coding
units 820c, 820d, and 820e. A processing order of a plurality of
coding units included in the first coding unit 800 may be a certain
order (e.g., a Z-scan order 830), and the image decoding apparatus
100 may determine whether the third coding units 820c, 820d, and
820e determined by splitting the right second coding unit 810b into
an odd number of coding units satisfy a condition that enables
processing in the certain order.
[0125] According to an embodiment, the image decoding apparatus 100
may determine whether the third coding units 820a and 820b, and
820c to 820e included in the first coding unit 800 satisfy the
condition that enables processing in the certain order, and the
condition relates to whether at least one of a width and height of
the second coding units 810a and 810b is split in half along a
boundary of the third coding units 820a and 820b, and 820c to 820e.
For example, the third coding units 820a and 820b determined when
the height of the left second coding unit 810a of the non-square
shape is split in half may satisfy the condition. It may be
determined that the third coding units 820c to 820e do not satisfy
the condition because the boundaries of the third coding units 820c
to 820e determined when the right second coding unit 810b is split
into three coding units are unable to split the width or height of
the right second coding unit 810b in half. When the condition is
not satisfied as described above, the image decoding apparatus 100
may determine disconnection of a scan order, and may determine that
the right second coding unit 810b is split into an odd number of
coding units, based on a result of the determination. According to
an embodiment, when a coding unit is split into an odd number of
coding units, the image decoding apparatus 100 may put a certain
restriction on a coding unit at a certain location from among the
split coding units. The restriction or the certain location has
been described above in relation to various embodiments, and thus
detailed descriptions thereof will not be provided herein.
[0126] FIG. 9 illustrates a process, performed by the image
decoding apparatus 100, of determining at least one coding unit by
splitting a first coding unit 900, according to an embodiment.
[0127] According to an embodiment, the image decoding apparatus 100
may split the first coding unit 900, based on at least one of block
shape information and information about a split shape mode, which
is obtained through the bitstream obtainer 110. The square first
coding unit 900 may be split into four square coding units, or may
be split into a plurality of non-square coding units. For example,
referring to FIG. 9, when the block shape information indicates
that the first coding unit 900 has a square shape and the
information about the split shape mode indicates to split the first
coding unit 900 into non-square coding units, the image decoding
apparatus 100 may split the first coding unit 900 into a plurality
of non-square coding units. In detail, when the information about
the split shape mode indicates to determine an odd number of coding
units by splitting the first coding unit 900 in a horizontal
direction or a vertical direction, the image decoding apparatus 100
may split the square first coding unit 900 into an odd number of
coding units, e.g., second coding units 910a, 910b, and 910c
determined by splitting the square first coding unit 900 in a
vertical direction or second coding units 920a, 920b, and 920c
determined by splitting the square first coding unit 900 in a
horizontal direction.
[0128] According to an embodiment, the image decoding apparatus 100
may determine whether the second coding units 910a, 910b, 910c,
920a, 920b, and 920c included in the first coding unit 900 satisfy
a condition for processing in a certain order, and the condition
relates to whether at least one of a width and height of the first
coding unit 900 is split in half along a boundary of the second
coding units 910a, 910b, 910c, 920a, 920b, and 920c. Referring to
FIG. 9, because boundaries of the second coding units 910a, 910b,
and 910c determined by splitting the square first coding unit 900
in a vertical direction do not split the width of the first coding
unit 900 in half, it may be determined that the first coding unit
900 does not satisfy the condition for processing in the certain
order. In addition, because boundaries of the second coding units
920a, 920b, and 920c determined by splitting the square first
coding unit 900 in a horizontal direction do not split the height
of the first coding unit 900 in half, it may be determined that the
first coding unit 900 does not satisfy the condition for processing
in the certain order. When the condition is not satisfied as
described above, the image decoding apparatus 100 may decide
disconnection of a scan order, and may determine that the first
coding unit 900 is split into an odd number of coding units, based
on a result of the decision. According to an embodiment, when a
coding unit is split into an odd number of coding units, the image
decoding apparatus 100 may put a certain restriction on a coding
unit at a certain location from among the split coding units. The
restriction or the certain location has been described above in
relation to various embodiments, and thus detailed descriptions
thereof will not be provided herein.
[0129] According to an embodiment, the image decoding apparatus 100
may determine various-shaped coding units by splitting a first
coding unit.
[0130] Referring to FIG. 9, the image decoding apparatus 100 may
split the square first coding unit 900 or a non-square first coding
unit 930 or 950 into various-shaped coding units.
[0131] FIG. 10 illustrates that a shape into which a second coding
unit is splittable is restricted when the second coding unit having
a non-square shape, which is determined as the image decoding
apparatus 100 splits a first coding unit 1000, satisfies a certain
condition, according to an embodiment.
[0132] According to an embodiment, the image decoding apparatus 100
may determine to split the square first coding unit 1000 into
non-square second coding units 1010a, and 1010b or 1020a and 1020b,
based on at least one of block shape information and information
about a split shape mode, which is obtained by the bitstream
obtainer 110. The second coding units 1010a and 1010b or 1020a and
1020b may be independently split. As such, the image decoding
apparatus 100 may determine to split or not to split each of the
second coding units 1010a and 1010b or 1020a and 1020b into a
plurality of coding units, based on at least one of block shape
information and information about a split shape mode of each of the
second coding units 1010a and 1010b or 1020a and 1020b. According
to an embodiment, the image decoding apparatus 100 may determine
third coding units 1012a and 1012b by splitting, in a horizontal
direction, the non-square left second coding unit 1010a, which is
determined by splitting the first coding unit 1000 in a vertical
direction. However, when the left second coding unit 1010a is split
in a horizontal direction, the image decoding apparatus 100 may
restrict the right second coding unit 1010b to not be split in a
horizontal direction in which the left second coding unit 1010a is
split. When third coding units 1014a and 1014b are determined by
splitting the right second coding unit 1010b in a same direction,
because the left and right second coding units 1010a and 1010b are
independently split in a horizontal direction, the third coding
units 1012a and 1012b or 1014a and 1014b may be determined.
However, this case serves equally as a case in which the image
decoding apparatus 100 splits the first coding unit 1000 into four
square second coding units 1030a, 1030b, 1030c, and 1030d, based on
at least one of the block shape information and the information
about the split shape mode, and may be inefficient in terms of
image decoding.
[0133] According to an embodiment, the image decoding apparatus 100
may determine third coding units 1022a and 1022b or 1024a and 1024b
by splitting, in a vertical direction, the non-square second coding
unit 1020a or 1020b determined by splitting the first coding unit
1000 in a horizontal direction. However, when a second coding unit
(e.g., the upper second coding unit 1020a) is split in a vertical
direction, for the above-described reason, the image decoding
apparatus 100 may restrict the other second coding unit (e.g., the
lower second coding unit 1020b) to not be split in a vertical
direction in which the upper second coding unit 1020a is split.
[0134] FIG. 11 illustrates a process, performed by the image
decoding apparatus 100, of splitting a square coding unit when
information about a split shape mode is unable to indicate that the
square coding unit is split into four square coding units,
according to an embodiment.
[0135] According to an embodiment, the image decoding apparatus 100
may determine second coding units 1110a and 1110b or 1120a and
1120b, etc. by splitting a first coding unit 1100, based on at
least one of block shape information and the information about the
split shape mode. The information about the split shape mode may
include information about various methods of splitting a coding
unit but, the information about various splitting methods may not
include information for splitting a coding unit into four square
coding units. According to the information about the split shape
mode, the image decoding apparatus 100 may not split the square
first coding unit 1100 into four square second coding units 1130a,
1130b, 1130c, and 1130d. The image decoding apparatus 100 may
determine the non-square second coding units 1110a and 1110b or
1120a and 1120b, etc., based on the information about the split
shape mode.
[0136] According to an embodiment, the image decoding apparatus 100
may independently split the non-square second coding units 1110a
and 1110b or 1120a and 1120b, etc. Each of the second coding units
1110a and 1110b or 1120a and 1120b, etc. may be recursively split
in a certain order, and this splitting method may correspond to a
method of splitting the first coding unit 1100, based on at least
one of block shape information and the information about the split
shape mode.
[0137] For example, the image decoding apparatus 100 may determine
square third coding units 1112a and 1112b by splitting the left
second coding unit 1110a in a horizontal direction, and may
determine square third coding units 1114a and 1114b by splitting
the right second coding unit 1110b in a horizontal direction.
Furthermore, the image decoding apparatus 100 may determine square
third coding units 1116a, 1116b, 1116c, and 1116d by splitting both
of the left and right second coding units 1110a and 1110b in a
horizontal direction. In this case, coding units having the same
shape as the four square second coding units 1130a, 1130b, 1130c,
and 1130d split from the first coding unit 1100 may be
determined.
[0138] As another example, the image decoding apparatus 100 may
determine square third coding units 1122a and 1122b by splitting
the upper second coding unit 1120a in a vertical direction, and may
determine square third coding units 1124a and 1124b by splitting
the lower second coding unit 1120b in a vertical direction.
Furthermore, the image decoding apparatus 100 may determine square
third coding units 1126a, 1126b, 1126c, and 1126d by splitting both
of the upper and lower second coding units 1120a and 1120b in a
vertical direction. In this case, coding units having the same
shape as the four square second coding units 1130a, 1130b, 1130c,
and 1130d split from the first coding unit 1100 may be
determined.
[0139] FIG. 12 illustrates that a processing order between a
plurality of coding units may be changed depending on a process of
splitting a coding unit, according to an embodiment.
[0140] According to an embodiment, the image decoding apparatus 100
may split a first coding unit 1200, based on the block shape
information and the information about the split shape mode. When
the block shape information indicates a square shape and the
information about the split shape mode indicates to split the first
coding unit 1200 in at least one of horizontal and vertical
directions, the image decoding apparatus 100 may determine second
coding units 1210a and 1210b or 1220a and 1220b, etc. by splitting
the first coding unit 1200. Referring to FIG. 12, the non-square
second coding units 1210a and 1210b or 1220a and 1220b determined
by splitting the first coding unit 1200 in only a horizontal
direction or vertical direction may be independently split based on
the block shape information and the information about the split
shape mode of each coding unit. For example, the image decoding
apparatus 100 may determine third coding units 1216a, 1216b, 1216c,
and 1216d by splitting, in a horizontal direction, the second
coding units 1210a and 1210b generated by splitting the first
coding unit 1200 in a vertical direction, and may determine third
coding units 1226a, 1226b, 1226c, and 1226d by splitting, in a
vertical direction, the second coding units 1220a and 1220b, which
are generated by splitting the first coding unit 1200 in a
horizontal direction. An operation of splitting the second coding
units 1210a and 1210b or 1220a and 1220b has been described above
in relation to FIG. 11, and thus detailed descriptions thereof will
not be provided herein.
[0141] According to an embodiment, the image decoding apparatus 100
may process coding units in a certain order. An operation of
processing coding units in a certain order has been described above
in relation to FIG. 7, and thus detailed descriptions thereof will
not be provided herein. Referring to FIG. 12, the image decoding
apparatus 100 may determine four square third coding units 1216a,
1216b, 1216c, and 1216d, and 1226a, 1226b, 1226c, and 1226d by
splitting the square first coding unit 1200. According to an
embodiment, the image decoding apparatus 100 may determine
processing orders of the third coding units 1216a, 1216b, 1216c,
and 1216d, and 1226a, 1226b, 1226c, and 1226d based on a splitting
method of the first coding unit 1200.
[0142] According to an embodiment, the image decoding apparatus 100
may determine the third coding units 1216a, 1216b, 1216c, and 1216d
by splitting, in a horizontal direction, the second coding units
1210a and 1210b generated by splitting the first coding unit 1200
in a vertical direction, and may process the third coding units
1216a, 1216b, 1216c, and 1216d in a processing order 1217 for
initially processing the third coding units 1216a and 1216c, which
are included in the left second coding unit 1210a, in a vertical
direction and then processing the third coding unit 1216b and
1216d, which are included in the right second coding unit 1210b, in
a vertical direction.
[0143] According to an embodiment, the image decoding apparatus 100
may determine the third coding units 1226a, 1226b, 1226c, and 1226d
by splitting, in a vertical direction, the second coding units
1220a and 1220b generated by splitting the first coding unit 1200
in a horizontal direction, and may process the third coding units
1226a, 1226b, 1226c, and 1226d in a processing order 1227 for
initially processing the third coding units 1226a and 1226b, which
are included in the upper second coding unit 1220a, in a horizontal
direction and then processing the third coding unit 1226c and
1226d, which are included in the lower second coding unit 1220b, in
a horizontal direction.
[0144] Referring to FIG. 12, the square third coding units 1216a,
1216b, 1216c, and 1216d, and 1226a, 1226b, 1226c, and 1226d may be
determined by splitting the second coding units 1210a and 1210b,
and 1220a and 1220b, respectively. Although the second coding units
1210a and 1210b are determined by splitting the first coding unit
1200 in a vertical direction differently from the second coding
units 1220a and 1220b which are determined by splitting the first
coding unit 1200 in a horizontal direction, the third coding units
1216a, 1216b, 1216c, and 1216d, and 1226a, 1226b, 1226c, and 1226d
split therefrom eventually show same-shaped coding units split from
the first coding unit 1200. Accordingly, by recursively splitting a
coding unit in different manners based on at least one of the block
shape information and the information about the split shape mode,
the image decoding apparatus 100 may process a plurality of coding
units in different orders even when the coding units are eventually
determined to be the same shape.
[0145] FIG. 13 illustrates a process of determining a depth of a
coding unit as a shape and size of the coding unit change, when the
coding unit is recursively split such that a plurality of coding
units are determined, according to an embodiment.
[0146] According to an embodiment, the image decoding apparatus 100
may determine the depth of the coding unit, based on a certain
criterion. For example, the certain criterion may be the length of
a long side of the coding unit. When the length of a long side of a
coding unit before being split is 2n times (n>0) the length of a
long side of a split current coding unit, the image decoding
apparatus 100 may determine that a depth of the current coding unit
is increased from a depth of the coding unit before being split, by
n. In the following description, a coding unit having an increased
depth is expressed as a coding unit of a lower depth.
[0147] Referring to FIG. 13, according to an embodiment, the image
decoding apparatus 100 may determine a second coding unit 1302 and
a third coding unit 1304 of lower depths by splitting a square
first coding unit 1300, based on block shape information indicating
a square shape (for example, the block shape information may be
expressed as `0: SQUARE`). Assuming that the size of the square
first coding unit 1300 is 2N.times.2N, the second coding unit 1302
determined by splitting a width and height of the first coding unit
1300 in 1/2 may have a size of N.times.N. Furthermore, the third
coding unit 1304 determined by splitting a width and height of the
second coding unit 1302 in 1/2 may have a size of N/2.times.N/2. In
this case, a width and height of the third coding unit 1304 are 1/4
times those of the first coding unit 1300. When a depth of the
first coding unit 1300 is D, a depth of the second coding unit
1302, the width and height of which are 1/2 times those of the
first coding unit 1300, may be D+1, and a depth of the third coding
unit 1304, the width and height of which are 1/4 times those of the
first coding unit 1300, may be D+2.
[0148] According to an embodiment, the image decoding apparatus 100
may determine a second coding unit 1312 or 1322 and a third coding
unit 1314 or 1324 of lower depths by splitting a non-square first
coding unit 1310 or 1320, based on block shape information
indicating a non-square shape (for example, the block shape
information may be expressed as `1: NS_VER` indicating a non-square
shape, a height of which is longer than a width, or as `2: NS_HOR`
indicating a non-square shape, a width of which is longer than a
height).
[0149] The image decoding apparatus 100 may determine a second
coding unit 1302, 1312, or 1322 by splitting at least one of a
width and height of the first coding unit 1310 having a size of
N.times.2N. In other words, the image decoding apparatus 100 may
determine the second coding unit 1302 having a size of N.times.N or
the second coding unit 1322 having a size of N.times.N/2 by
splitting the first coding unit 1310 in a horizontal direction, or
may determine the second coding unit 1312 having a size of
N/2.times.N by splitting the first coding unit 1310 in horizontal
and vertical directions.
[0150] According to an embodiment, the image decoding apparatus 100
may determine the second coding unit 1302, 1312, or 1322 by
splitting at least one of a width and height of the first coding
unit 1320 having a size of 2N.times.N. That is, the image decoding
apparatus 100 may determine the second coding unit 1302 having a
size of N.times.N or the second coding unit 1312 having a size of
N/2.times.N by splitting the first coding unit 1320 in a vertical
direction, or may determine the second coding unit 1322 having a
size of N.times.N/2 by splitting the first coding unit 1320 in
horizontal and vertical directions.
[0151] According to an embodiment, the image decoding apparatus 100
may determine a third coding unit 1304, 1314, or 1324 by splitting
at least one of a width and height of the second coding unit 1302
having a size of N.times.N. That is, the image decoding apparatus
100 may determine the third coding unit 1304 having a size of
N/2.times.N/2, the third coding unit 1314 having a size of
N/4.times.N/2, or the third coding unit 1324 having a size of
N/2.times.N/4 by splitting the second coding unit 1302 in vertical
and horizontal directions.
[0152] According to an embodiment, the image decoding apparatus 100
may determine the third coding unit 1304, 1314, or 1324 by
splitting at least one of a width and height of the second coding
unit 1312 having a size of N/2.times.N. That is, the image decoding
apparatus 100 may determine the third coding unit 1304 having a
size of N/2.times.N/2 or the third coding unit 1324 having a size
of N/2.times.N/4 by splitting the second coding unit 1312 in a
horizontal direction, or may determine the third coding unit 1314
having a size of N/4.times.N/2 by splitting the second coding unit
1312 in vertical and horizontal directions.
[0153] According to an embodiment, the image decoding apparatus 100
may determine the third coding unit 1304, 1314, or 1324 by
splitting at least one of a width and height of the second coding
unit 1322 having a size of N.times.N/2. That is, the image decoding
apparatus 100 may determine the third coding unit 1304 having a
size of N/2.times.N/2 or the third coding unit 1314 having a size
of N/4.times.N/2 by splitting the second coding unit 1322 in a
vertical direction, or may determine the third coding unit 1324
having a size of N/2.times.N/4 by splitting the second coding unit
1322 in vertical and horizontal directions.
[0154] According to an embodiment, the image decoding apparatus 100
may split the square coding unit 1300, 1302, or 1304 in a
horizontal or vertical direction. For example, the image decoding
apparatus 100 may determine the first coding unit 1310 having a
size of N.times.2N by splitting the first coding unit 1300 having a
size of 2N.times.2N in a vertical direction, or may determine the
first coding unit 1320 having a size of 2N.times.N by splitting the
first coding unit 1300 in a horizontal direction. According to an
embodiment, when a depth is determined based on the length of the
longest side of a coding unit, a depth of a coding unit determined
by splitting the first coding unit 1300 having a size of
2N.times.2N in a horizontal or vertical direction may be the same
as the depth of the first coding unit 1300.
[0155] According to an embodiment, a width and height of the third
coding unit 1314 or 1324 may be 1/4 times those of the first coding
unit 1310 or 1320. When a depth of the first coding unit 1310 or
1320 is D, a depth of the second coding unit 1312 or 1322, the
width and height of which are 1/2 times those of the first coding
unit 1310 or 1320, may be D+1, and a depth of the third coding unit
1314 or 1324, the width and height of which are 1/4 times those of
the first coding unit 1310 or 1320, may be D+2.
[0156] FIG. 14 illustrates depths that are determinable based on
shapes and sizes of coding units, and part indexes (PIDs) that are
for distinguishing the coding units, according to an
embodiment.
[0157] According to an embodiment, the image decoding apparatus 100
may determine various-shaped second coding units by splitting a
square first coding unit 1400. Referring to FIG. 14, the image
decoding apparatus 100 may determine second coding units 1402a and
1402b, 1404a and 1404b, and 1406a, 1406b, 1406c, and 1406d by
splitting the first coding unit 1400 in at least one of vertical
and horizontal directions based on information about a split shape
mode. That is, the image decoding apparatus 100 may determine the
second coding units 1402a and 1402b, 1404a and 1404b, and 1406a,
1406b, 1406c, and 1406d, based on the information about the split
shape mode of the first coding unit 1400.
[0158] According to an embodiment, depths of the second coding
units 1402a and 1402b, 1404a and 1404b, and 1406a, 1406b, 1406c,
and 1406d, which are determined based on the information about the
split shape mode of the square first coding unit 1400, may be
determined based on the length of a long side thereof. For example,
because the length of a side of the square first coding unit 1400
equals the length of a long side of the non-square second coding
units 1402a and 1402b, and 1404a and 1404b, the first coding unit
2100 and the non-square second coding units 1402a and 1402b, and
1404a and 1404b may have the same depth, e.g., D. However, when the
image decoding apparatus 100 splits the first coding unit 1400 into
the four square second coding units 1406a, 1406b, 1406c, and 1406d,
based on the information about the split shape mode, because the
length of a side of the square second coding units 1406a, 1406b,
1406c, and 1406d is 1/2 times the length of a side of the first
coding unit 1400, a depth of the second coding units 1406a, 1406b,
1406c, and 1406d may be D+1 which is lower than the depth D of the
first coding unit 1400 by 1.
[0159] According to an embodiment, the image decoding apparatus 100
may determine a plurality of second coding units 1412a and 1412b,
and 1414a, 1414b, and 1414c by splitting a first coding unit 1410,
a height of which is longer than a width, in a horizontal direction
based on the information about the split shape mode. According to
an embodiment, the image decoding apparatus 100 may determine a
plurality of second coding units 1422a and 1422b, and 1424a, 1424b,
and 1424c by splitting a first coding unit 1420, a width of which
is longer than a height, in a vertical direction based on the
information about the split shape mode.
[0160] According to an embodiment, a depth of the second coding
units 1412a and 1412b, and 1414a, 1414b, and 1414c, or 1422a and
1422b, and 1424a, 1424b, and 1424c, which are determined based on
the information about the split shape mode of the non-square first
coding unit 1410 or 1420, may be determined based on the length of
a long side thereof. For example, because the length of a side of
the square second coding units 1412a and 1412b is 1/2 times the
length of a side of the non-square first coding unit 1410, a height
of which is longer than a width, a depth of the square second
coding units 1412a and 1412b is D+1 which is lower than the depth D
of the non-square first coding unit 1410 by 1.
[0161] Furthermore, the image decoding apparatus 100 may split the
non-square first coding unit 1410 into an odd number of second
coding units 1414a, 1414b, and 1414c, based on the information
about the split shape mode. The odd number of second coding units
1414a, 1414b, and 1414c may include the non-square second coding
units 1414a and 1414c and the square second coding unit 1414b. In
this case, because the length of a long side of the non-square
second coding units 1414a and 1414c and the length of a side of the
square second coding unit 1414b are 1/2 times the length of a side
of the first coding unit 1410, a depth of the second coding units
1414a, 1414b, and 1414c may be D+1 which is lower than the depth D
of the non-square first coding unit 1410 by 1. The image decoding
apparatus 100 may determine depths of coding units split from the
non-square first coding unit 1420, a width of which is longer than
a height, by using the above-described method of determining depths
of coding units split from the first coding unit 1410.
[0162] According to an embodiment, the image decoding apparatus 100
may determine PIDs for identifying split coding units, based on a
size ratio between the coding units, when an odd number of split
coding units do not have equal sizes. Referring to FIG. 14, a
coding unit 1414b at a center location among the odd number of
split coding units 1414a, 1414b, and 1414c may have a width equal
to that of the other coding units 1414a and 1414c and may have a
height which is two times that of the other coding units 1414a and
1414c. In other words, in this case, the coding unit 1414b at the
center location may include two of the other coding unit 1414a or
1414c. Therefore, when a PID of the coding unit 1414b at the center
location is 1 based on a scan order, a PID of the coding unit 1414c
located next to the coding unit 1414b may be increased by 2 and
thus may be 3. That is, discontinuity in PID values may be present.
According to an embodiment, the image decoding apparatus 100 may
determine whether an odd number of split coding units do not have
equal sizes, based on whether discontinuity is present in PIDs for
identifying the split coding units.
[0163] According to an embodiment, the image decoding apparatus 100
may determine whether to use a specific splitting method, based on
PID values for identifying a plurality of coding units determined
by splitting a current coding unit. Referring to FIG. 14, the image
decoding apparatus 100 may determine an even number of coding units
1412a and 1412b or an odd number of coding units 1414a, 1414b, and
1414c by splitting the first coding unit 1410 having a rectangular
shape, a height of which is longer than a width. The image decoding
apparatus 100 may use respective PIDs indicating the plurality of
coding units so as to identify the plurality of coding units.
According to an embodiment, the PID may be obtained from a sample
of a certain location of each coding unit (e.g., an upper left
sample).
[0164] According to an embodiment, the image decoding apparatus 100
may determine a coding unit at a certain location from among the
split coding units, by using the PIDs for distinguishing the coding
units. According to an embodiment, when the information about the
split shape mode of the first coding unit 1410 having a rectangular
shape, a height of which is longer than a width, indicates to split
a coding unit into three coding units, the image decoding apparatus
100 may split the first coding unit 1410 into three coding units
1414a, 1414b, and 1414c. The image decoding apparatus 100 may
assign a PID to each of the three coding units 1414a, 1414b, and
1414c. The image decoding apparatus 100 may compare respective PIDs
of an odd number of split coding units with one another in order to
determine a coding unit at a center location from among the odd
number of coding units. The image decoding apparatus 100 may
determine the coding unit 1414b having a PID corresponding to a
middle value among the PIDs of the coding units, as the coding unit
at the center location from among the coding units determined by
splitting the first coding unit 1410. According to an embodiment,
the image decoding apparatus 100 may determine PIDs for
distinguishing split coding units, based on a size ratio between
the coding units, when the split coding units do not have equal
sizes. Referring to FIG. 14, the coding unit 1414b generated by
splitting the first coding unit 1410 may have a width equal to that
of the other coding units 1414a and 1414c, but may have a height
which is two times that of the other coding units 1414a and 1414c.
In this case, when the PID of the coding unit 1414b at the center
location is 1, the PID of the coding unit 1414c located next to the
coding unit 1414b may be increased by 2 and thus may be 3. When the
PID is not uniformly increased as described above, the image
decoding apparatus 100 may determine that a coding unit is split
into a plurality of coding units including a coding unit having a
size different from that of the other coding units. According to an
embodiment, when the information about the split shape mode
indicates to split a coding unit into an odd number of coding
units, the image decoding apparatus 100 may split a current coding
unit in such a manner that a coding unit at a certain location from
among an odd number of coding units (e.g., a coding unit at a
center location) has a size different from that of the other coding
units. In this case, the image decoding apparatus 100 may determine
the coding unit located at the center location and having a
different size, by using the PI Ds of the coding units. However,
the PIDs and the size or location of the coding unit of the certain
location are not limited to the above-described examples, and
various PI Ds and various locations and sizes of coding units may
be used.
[0165] According to an embodiment, the image decoding apparatus 100
may use a certain data unit where a coding unit starts to be
recursively split.
[0166] FIG. 15 illustrates that a plurality of coding units are
determined based on a plurality of certain data units included in a
picture, according to an embodiment.
[0167] According to an embodiment, a certain data unit may be
defined as a data unit where a coding unit starts to be recursively
split by using at least one of the block shape information and the
information about the split shape mode. That is, the certain data
unit may correspond to a coding unit of an uppermost depth, which
is used to determine a plurality of coding units split from a
current picture. In the following descriptions, for convenience of
explanation, the certain data unit is referred to as a reference
data unit.
[0168] According to an embodiment, the reference data unit may have
a certain size and a certain shape. According to an embodiment, the
reference data unit may include M.times.N samples. Herein, M and N
may be equal to each other, and may be integers expressed as powers
of 2. That is, the reference data unit may have a square or
non-square shape, and may be split into an integer number of coding
units.
[0169] According to an embodiment, the image decoding apparatus 100
may split the current picture into a plurality of reference data
units. According to an embodiment, the image decoding apparatus 100
may split the plurality of reference data units split from the
current picture, by using the information about the split shape
mode of each of the plurality of reference data units. The
operation of splitting the reference data unit may correspond to a
splitting operation using a quadtree structure.
[0170] According to an embodiment, the image decoding apparatus 100
may previously determine a minimum size allowed for the reference
data units included in the current picture. Accordingly, the image
decoding apparatus 100 may determine reference data units having
various sizes equal to or greater than the minimum size, and may
determine one or more coding units by using the block shape
information and the information about the split shape mode with
reference to the determined reference data units.
[0171] Referring to FIG. 15, the image decoding apparatus 100 may
use a square reference coding unit 1500 or a non-square reference
coding unit 1502. According to an embodiment, the shape and size of
a reference coding unit may be determined based on various data
units capable of including one or more reference coding units
(e.g., a sequence, a picture, a slice, a slice segment, a largest
coding units, and the like).
[0172] According to an embodiment, the bitstream obtainer 110 of
the image decoding apparatus 100 may obtain, from a bitstream, at
least one of reference coding unit shape information and reference
coding unit size information for each of the various data units. An
operation of splitting the square reference coding unit 1500 into
one or more coding units has been described above in relation to
the operation of splitting the current coding unit 300 of FIG. 3,
and an operation of splitting the non-square reference coding unit
1502 into one or more coding units has been described above in
relation to the operation of splitting the current coding unit 400
or 450 of FIG. 4. Thus, detailed descriptions thereof will not be
provided herein.
[0173] According to an embodiment, the image decoding apparatus 100
may use a PID for identifying the size and shape of reference
coding units, to determine the size and shape of reference coding
units according to some data units previously determined based on a
certain condition. That is, the bitstream obtainer 110 may obtain,
from the bitstream, only the PID for identifying the size and shape
of reference coding units, for each slice, slice segment, or
largest coding unit which is a data unit satisfying a certain
condition (e.g., a data unit having a size equal to or smaller than
a slice) among the various data units (e.g., a sequence, a picture,
a slice, a slice segment, a largest coding unit, and the like). The
image decoding apparatus 100 may determine the size and shape of
reference data units for each data unit that satisfies the certain
condition, by using the PID. When the reference coding unit shape
information and the reference coding unit size information are
obtained and used from the bitstream for each data unit having a
relatively small size, efficiency of using the bitstream may not be
high, and therefore, only the PID may be obtained and used instead
of directly obtaining the reference coding unit shape information
and the reference coding unit size information. In this case, at
least one of the size and shape of reference coding units
corresponding to the PID for identifying the size and shape of
reference coding units may be previously determined. That is, the
image decoding apparatus 100 may determine at least one of the size
and shape of reference coding units included in a data unit serving
as a basis for obtaining the PID, by selecting the previously
determined at least one of the size and shape of reference coding
units according to the PID.
[0174] According to an embodiment, the image decoding apparatus 100
may use one or more reference coding units included in a largest
coding unit. That is, a largest coding unit split from an image may
include one or more reference coding units, and coding units may be
determined by recursively splitting each reference coding unit.
According to an embodiment, at least one of a width and height of
the largest coding unit may be integer times at least one of the
width and height of each reference coding unit. According to an
embodiment, the size of reference coding units may be obtained by
splitting the largest coding unit n times based on a quadtree
structure. That is, the image decoding apparatus 100 may determine
the reference coding units by splitting the largest coding unit n
times based on a quadtree structure, and may split the reference
coding unit based on at least one of the block shape information
and the information about the split shape mode according to various
embodiments.
[0175] FIG. 16 illustrates a processing block serving as a
criterion for determining a determination order of reference coding
units included in a picture 1600, according to an embodiment.
[0176] According to an embodiment, the image decoding apparatus 100
may determine one or more processing blocks split from a picture.
The processing block is a data unit including one or more reference
coding units split from an image, and the one or more reference
coding units included in the processing block may be determined
according to a specific order. That is, a determination order of
one or more reference coding units determined in each processing
block may correspond to one of various types of orders for
determining reference coding units, and may vary depending on the
processing block. The determination order of reference coding
units, which is determined with respect to each processing block,
may be one of various orders, e.g., raster scan order, Z-scan,
N-scan, up-right diagonal scan, horizontal scan, and vertical scan,
but is not limited to the aforementioned scan orders.
[0177] According to an embodiment, the image decoding apparatus 100
may obtain processing block size information and may determine the
size of one or more processing blocks included in the image. The
image decoding apparatus 100 may obtain the processing block size
information from a bitstream and may determine the size of one or
more processing blocks included in the image. The size of
processing blocks may be a certain size of data units, which is
indicated by the processing block size information.
[0178] According to an embodiment, the bitstream obtainer 110 of
the image decoding apparatus 100 may obtain the processing block
size information from the bitstream for each specific data unit.
For example, the processing block size information may be obtained
from the bitstream in a data unit such as an image, sequence,
picture, slice, or slice segment. That is, the bitstream obtainer
110 may obtain the processing block size information from the
bitstream according to each of the various data units, and the
image decoding apparatus 100 may determine the size of one or more
processing blocks, which are split from the picture, by using the
obtained processing block size information. The size of the
processing blocks may be integer times that of a reference coding
unit.
[0179] According to an embodiment, the image decoding apparatus 100
may determine the size of processing blocks 1602 and 1612 included
in the picture 1600. For example, the image decoding apparatus 100
may determine the size of processing blocks, based on the
processing block size information obtained from the bitstream.
Referring to FIG. 16, according to an embodiment, the image
decoding apparatus 100 may determine a width of the processing
blocks 1602 and 1612 to be four times the width of the reference
coding units, and may determine a height of the processing blocks
1602 and 1612 to be four times the height of the reference coding
units. The image decoding apparatus 100 may determine a
determination order of one or more reference coding units in one or
more processing blocks.
[0180] According to an embodiment, the image decoding apparatus 100
may determine the processing blocks 1602 and 1612, which are
included in the picture 1600, based on the size of processing
blocks, and may determine a determination order of one or more
reference coding units included in the processing blocks 1602 and
1612. According to an embodiment, determination of reference coding
units may include determination of the size of the reference coding
units.
[0181] According to an embodiment, the image decoding apparatus 100
may obtain, from the bitstream, determination order information of
one or more reference coding units included in one or more
processing blocks, and may determine a determination order of one
or more reference coding units, based on the obtained determination
order information. The determination order information may be
defined as an order or direction for determining the reference
coding units in the processing block. That is, the determination
order of reference coding units may be independently determined for
each processing block.
[0182] According to an embodiment, the image decoding apparatus 100
may obtain, from the bitstream, the determination order information
of reference coding units for each specific data unit. For example,
the bitstream obtainer 110 may obtain the determination order
information of reference coding units from the bitstream for each
data unit such as an image, sequence, picture, slice, slice
segment, or processing block. Because the determination order
information of reference coding units indicates an order for
determining reference coding units in a processing block, the
determination order information may be obtained for each specific
data unit including an integer number of processing blocks.
[0183] According to an embodiment, the image decoding apparatus 100
may determine one or more reference coding units based on the
determined determination order.
[0184] According to an embodiment, the bitstream obtainer 110 may
obtain from the bitstream the determination order information of
reference coding units, as information related to the processing
blocks 1602 and 1612, and the image decoding apparatus 100 may
determine a determination order of one or more reference coding
units included in the processing blocks 1602 and 1612 and determine
one or more reference coding units, which are included in the
picture 1600, based on the determination order. Referring to FIG.
16, the image decoding apparatus 100 may determine determination
orders 1604 and 1614 of one or more reference coding units related
to the processing blocks 1602 and 1612, respectively. For example,
when the determination order information of reference coding units
is obtained for each processing block, different types of the
determination order information of reference coding units may be
obtained for the processing blocks 1602 and 1612. When the
determination order 1604 of reference coding units in the
processing block 1602 is a raster scan order, reference coding
units included in the processing block 1602 may be determined
according to a raster scan order. On the contrary, when the
determination order 1614 of reference coding units in the other
processing block 1612 is a backward raster scan order, reference
coding units included in the processing block 1612 may be
determined according to the backward raster scan order.
[0185] According to an embodiment, the image decoding apparatus 100
may decode the determined one or more reference coding units. The
image decoding apparatus 100 may decode an image, based on the
reference coding units determined through the above-described
embodiments. A method of decoding the reference coding units may
include various image decoding methods.
[0186] According to an embodiment, the image decoding apparatus 100
may obtain block shape information indicating the shape of a
current coding unit or the information about the split shape mode
indicating a splitting method of the current coding unit, from the
bitstream, and may use the obtained information. The block shape
information or the information about the split shape mode may be
included in the bitstream related to various data units. For
example, the image decoding apparatus 100 may use the block shape
information or the information about the split shape mode included
in a sequence parameter set, a picture parameter set, a video
parameter set, a slice header, or a slice segment header.
Furthermore, the image decoding apparatus 100 may obtain, from the
bitstream, a syntax element corresponding to the block shape
information or the information about the split shape mode, for each
largest coding unit, each reference coding unit, or each processing
block, and may use the obtained syntax element.
[0187] FIG. 17 illustrates coding units that may be determined for
each picture when a combination of shapes into which a coding unit
is splittable is different for each picture, according to an
embodiment.
[0188] Referring to FIG. 17, the image decoding apparatus 100 may
determine a combination of split shapes into which a coding unit is
splittable to be different for each picture. For example, the image
decoding apparatus 100 may decode an image by using a picture 1700
splittable into 4 coding units, a picture 1710 splittable into 2 or
4 coding units, and a picture 1720 splittable into 2, 3, or 4
coding units, among one or more pictures included in the image. The
image decoding apparatus 100 may only use split shape information
indicating a split into 4 square coding units, in order to split
the picture 1700 into a plurality of coding units. The image
decoding apparatus 100 may only use split shape information
indicating a split into 2 or 4 coding units, in order to split the
picture 1710. The image decoding apparatus 100 may only use split
shape information indicating a split into 2, 3, or 4 coding units,
in order to split the picture 1720. Because the above combinations
of split shapes are only embodiments for describing operations of
the image decoding apparatus 100, the combinations of split shapes
should not be interpreted limitedly to the embodiments and it
should be interpreted that various types of combinations of split
shapes may be used for each of certain data units.
[0189] According to an embodiment, the bitstream obtainer 110 of
the image decoding apparatus 100 may obtain a bitstream including
an index indicating a combination of split shape information, for
each of certain data units (for example, a sequence, a picture, or
slice). For example, the bitstream obtainer 110 may obtain an index
indicating a combination of split shape information from a sequence
parameter set, a picture parameter set, or a slice header. The
image decoding apparatus 100 may determine a combination of split
shapes of coding units into which a certain data unit is splittable
by using the obtained index, and accordingly, different
combinations of split shapes may be used for each of certain data
units.
[0190] FIG. 18 illustrates various shapes of a coding unit that may
be determined based on split shape information representable in a
binary code, according to an embodiment.
[0191] According to an embodiment, the image decoding apparatus 100
may split a coding unit into various shapes by using block shape
information and split shape information obtained via the bitstream
obtainer 110. Splittable shapes of a coding unit may correspond to
various shapes including the shapes described above through the
above-described embodiments.
[0192] Referring to FIG. 18, the image decoding apparatus 100 may
split a square coding unit in at least one of a horizontal
direction and a vertical direction, based on the split shape
information, and split a non-square coding unit in a horizontal
direction or a vertical direction.
[0193] According to an embodiment, when the image decoding
apparatus 100 is capable of splitting a square coding unit in a
horizontal direction and a vertical direction to obtain 4 square
coding units, 4 split shapes may be indicated by the split shape
information of the square coding unit. According to an embodiment,
the split shape information may be represented as a 2-digit binary
code, and a binary code may be assigned for each split shape. For
example, when a coding unit is not split, the split shape
information may be represented as (00)b, when a coding unit is
split in a horizontal direction and a vertical direction, the split
shape information may be represented as (01)b, when a coding unit
is split in a horizontal direction, the split shape information may
be represented as (10)b, and when a coding unit is split in a
vertical direction, the split shape information may be represented
as (11)b.
[0194] According to an embodiment, when the image decoding
apparatus 100 splits a non-square coding unit in a horizontal
direction or a vertical direction, a type of split shape indicated
by the split shape information may be determined based on the split
number of coding units. Referring to FIG. 18, the image decoding
apparatus 100 may split the non-square coding unit into up to 3
coding units, according to an embodiment. The image decoding
apparatus 100 may split a coding unit into two coding units and in
this case, the split shape information may be represented as (10)b.
The image decoding apparatus 100 may split a coding unit into three
coding units and in this case, the split shape information may be
represented as (11)b. The image decoding apparatus 100 may
determine not to split a coding unit and in this case, the split
shape information may be represented as (0)b. In otherwords, the
image decoding apparatus 100 may use variable length coding (VLC)
instead of fixed length coding (FLC) so as to use a binary code
indicating the split shape information.
[0195] According to an embodiment, referring to FIG. 18, a binary
code of the split shape information indicating that a coding unit
is not split may be represented as (0)b. When a binary code of the
split shape information indicating that a coding unit is not split
is set to (00)b, binary codes of two bits of split shape
information need to be all used despite that there is no split
shape information set as (01)b. However, as shown in FIG. 18, when
3 types of split shapes are used for a non-square coding unit, the
image decoding apparatus 100 is able to determine that a coding
unit is not split even when using one-bit binary code (0)b as the
split shape information, and thus a bitstream may be efficiently
used. However, split shapes of a non-square coding unit indicated
by the split shape information should not be interpreted limitedly
to 3 shapes described with reference to FIG. 18, and should be
interpreted as various shapes including the above-described
embodiments.
[0196] FIG. 19 illustrates other shapes of a coding unit that may
be determined based on split shape information representable in a
binary code, according to an embodiment.
[0197] Referring to FIG. 19, the image decoding apparatus 100 may
split a square coding unit in a horizontal direction or a vertical
direction, based on the split shape information, and may split a
non-square coding unit in a horizontal direction or a vertical
direction. In otherwords, the split shape information may indicate
that a square coding unit is split in one direction. In this case,
a binary code of split shape information indicating that a square
coding unit is not split may be represented as (0)b. When a binary
code of the split shape information indicating that a coding unit
is not split is set to (00)b, binary codes of two bits of split
shape information need to be all used despite that there is no
split shape information set as (01)b. However, as shown in FIG. 19,
when 3 types of split shapes are used for a square coding unit, the
image decoding apparatus 100 is able to determine that a coding
unit is not split even when using one-bit binary code (0)b as the
split shape information, and thus a bitstream may be efficiently
used. However, split shapes of a square coding unit indicated by
the split shape information should not be interpreted limitedly to
3 shapes described with reference to FIG. 19, and should be
interpreted as various shapes including the above-described
embodiments.
[0198] According to an embodiment, block shape information or split
shape information may be represented by using a binary code, and
such information may be immediately generated as a bitstream.
Alternatively, the block shape information or split shape
information represented in a binary code may be used as a binary
code input during context adaptive binary arithmetic coding (CABAC)
without being immediately generated as a bitstream.
[0199] According to an embodiment, a process in which the image
decoding apparatus 100 obtains syntax regarding block shape
information or split shape information via CABAC will be described.
A bitstream including a binary code of the syntax may be obtained
via the bitstream obtainer 110. The image decoding apparatus 100
may detect a syntax element indicating block shape information or
split shape information by inverse-binarizing a bin string included
in the obtained bitstream. According to an embodiment, the image
decoding apparatus 100 may obtain a set of binary bin strings
corresponding to a syntax element to be decoded, and may decode
each bin by using probability information, and may repeat such
operations until a bin string including the decoded bins becomes
the same as one of previously obtained bin strings. The image
decoding apparatus 100 may determine the syntax element by
performing inverse binarization on the bin string.
[0200] According to an embodiment, the image decoding apparatus 100
may determine the syntax for the bin string by performing a
decoding process of adaptive binary arithmetic coding, and update a
probability model for the bins obtained via the bitstream obtainer
110. Referring to FIG. 18, the bitstream obtainer 110 of the image
decoding apparatus 100 may obtain the bitstream indicating the
binary code indicating the split shape information, according to an
embodiment. The image decoding apparatus 100 may determine the
syntax for the split shape information by using the binary code
having a size of 1 bit or 2 bits. The image decoding apparatus 100
may update a probability for each bit among the 2-bit binary code
so as to determine the syntax for the split shape information. In
other words, the image decoding apparatus 100 may update a
probability of having a value of 0 or 1 when decoding a next bin,
based on whether a value of a first bin among the 2-bit binary code
is 0 or 1.
[0201] According to an embodiment, the image decoding apparatus 100
may update, while determining syntax, a probability for bins used
while decoding bins of a bin string for the syntax, and may
determine that certain bits of the bin string have the same
probability without updating the probability.
[0202] Referring to FIG. 18, while determining syntax by using a
bin string indicating split shape information for a non-square
coding unit, the image decoding apparatus 100 may determine the
syntax for the split shape information by using one bin having a
value of 0 when the non-square coding unit is not split. In other
words, when block shape information indicates that a current coding
unit has a non-square shape, a first bin of a bin string for split
shape mode information may be 0 when a non-square coding unit is
not split and may be 1 when the non-square coding unit is split
into 2 or 3 coding units. Accordingly, a probability that the first
bin of the bin string of the split shape information for the
non-square coding unit is 0 may be 1/3, and a probability that the
first bin of the bin string of the split shape information for the
non-square coding unit is 1 may be 2/3. As described above, because
split shape mode information indicating that a non-square coding
unit is not split may represent only a 1-bit bin string having a
value of 0, the image decoding apparatus 100 may determine syntax
for the split shape information by determining whether a second bin
is 0 or 1 only when a first bin of the split shape information is
1. According to an embodiment, when the first bin of the split
shape information is 1, the image decoding apparatus 100 may decode
bins considering that probabilities of the second bin being 0 and 1
are the same.
[0203] According to an embodiment, the image decoding apparatus 100
may use various probabilities for each bin while determining the
bins of the bin string for the split shape information. According
to an embodiment, the image decoding apparatus 100 may differently
determine the probabilities of the bins for the split shape
information, based on a direction of a non-square block. According
to an embodiment, the image decoding apparatus 100 may differently
determine the probabilities of the bins for the split shape
information, based on an area of a current coding unit or a length
of a long side of the current coding unit. According to an
embodiment, the image decoding apparatus 100 may differently
determine the probabilities of the bins for the split shape
information, based on at least one of the area of the current
coding unit or the length of a long side of the current coding
unit.
[0204] According to an embodiment, the image decoding apparatus 100
may determine that probabilities of bins for split shape
information are the same with respect to coding units of a certain
size or greater. For example, it may be determined that the
probabilities of the bins for the split shape information are the
same for coding units of a size of 64 samples or greater, based on
the length of a long side of the coding unit.
[0205] According to an embodiment, the image decoding apparatus 100
may determine initial probabilities of the bins included in the bin
string of the split shape information, based on a slice type (for
example, an I-slice, a P-slice, or a B-slice).
[0206] FIG. 20 is a block diagram of an image encoding and decoding
system 2000 that performs loop filtering.
[0207] An encoding end 2010 of the image encoding and decoding
system 2000 transmits an encoded bitstream of an image, and a
decoding end 2050 thereof outputs a reconstructed image by
receiving and decoding the bitstream. Here, the encoding end 2010
may have a similar configuration to the image encoding apparatus
200, which will be described later, and the decoding end 2050 may
have a similar configuration to the image decoding apparatus
100.
[0208] At the encoding end 2010, a prediction encoder 2015 outputs
a reference image via inter prediction and intra prediction, and a
transformer and quantizer 2020 transforms and quantizes residual
data between the reference image and a current input image to a
quantized transform coefficient and outputs the quantized transform
coefficient. An entropy encoder 2025 encodes the quantized
transform coefficient, and outputs the encoded quantized transform
coefficient as a bitstream. The quantized transform coefficient is
reconstructed as data of a spatial domain via an inverse quantizer
and inverse transformer 2030, and the data of the spatial domain is
output as a reconstructed image via a deblocking filter 2035 and a
loop filter 2040. The reconstructed image may be used as a
reference image of a next input image via the prediction encoder
2015.
[0209] Encoded image data among the bitstream received by the
decoding end 2050 is reconstructed as residual data of a spatial
domain via an entropy decoder 2055 and an inverse quantizer and
inverse transformer 2060. Image data of a spatial domain is
configured when a reference image and residual data output from a
prediction decoder 2075 are combined, and a deblocking filter 2065
and a loop filter 2070 may output a reconstructed image regarding a
current original image by performing filtering on the image data of
the spatial domain. The reconstructed image may be used by the
prediction decoder 2075, as a reference image for a next original
image.
[0210] The loop filter 2040 of the encoding end 2010 performs loop
filtering by using filter information input according to a user
input or system settings. The filter information used by the loop
filter 2040 is output to the encoding end 2010 and transmitted to
the decoding end 2050 together with the encoded image data. The
loop filter 2070 of the decoding end 2050 may perform loop
filtering based on the filter information input from the decoding
end 2050.
[0211] The above-described various embodiments describe operations
related to an image decoding method performed by the image decoding
apparatus 100. Hereinafter, operations of the image encoding
apparatus 200 performing an image encoding method corresponding to
an inverse procedure of the image decoding method will be described
via various embodiments.
[0212] FIG. 2 is a block diagram of the image encoding apparatus
200 capable of encoding an image, based on at least one of block
shape information and split shape information, according to an
embodiment.
[0213] The image encoding apparatus 200 may include an encoder 220
and a bitstream generator 210. The encoder 220 may receive an input
image and encode the input image. The encoder 220 may obtain at
least one syntax element by encoding the input image. The syntax
element may include at least one of a skip flag, a prediction mode,
a motion vector difference, a motion vector prediction method (or
index), a transform quantized coefficient, a coded block pattern, a
coded block flag, an intra prediction mode, a direct flag, a merge
flag, a delta QP, a reference index, a prediction direction, and a
transform index. The encoder 220 may determine a context model,
based on block shape information including at least one of a shape,
direction, ratio of width and height, or size of a coding unit.
[0214] The bitstream generator 210 may generate a bitstream, based
on the encoded input image. For example, the bitstream generator
210 may generate the bitstream by entropy-encoding the syntax
element, based on the context model. Also, the image encoding
apparatus 200 may transmit the bitstream to the image decoding
apparatus 100.
[0215] According to an embodiment, the encoder 220 of the image
encoding apparatus 200 may determine a shape of a coding unit. For
example, the coding unit may have a square shape or a non-share
shape, and information indicating such a shape may be included in
block shape information.
[0216] According to an embodiment, the encoder 220 may determine in
which shape a coding unit is to be split. The encoder 220 may
determine a shape of at least one coding unit included in the
coding unit, and the bitstream generator 210 may generate a
bitstream including split shape information including information
about such a shape of the coding unit.
[0217] According to an embodiment, the encoder 220 may determine
whether a coding unit is to be split or not to be split. When the
encoder 220 determines that only one coding unit is included in the
coding unit or that the coding unit is not split, the bitstream
generator 210 may generate a bitstream including split shape
information indicating that the coding unit is not split. Also, the
encoder 220 may split the coding unit into a plurality of coding
units, and the bitstream generator 210 may generate the bitstream
including split shape information indicating that the coding unit
is split into the plurality of coding units.
[0218] According to an embodiment, information indicating the
number of coding units into which the coding unit is to be split or
a direction of splitting the coding unit may be included in the
split shape information. For example, the split shape information
may indicate that the coding unit is split in at least one of a
vertical direction and a horizontal direction or is not split.
[0219] The image encoding apparatus 200 determines information
about a split shape mode, based on a split shape mode of a coding
unit. The image encoding apparatus 200 may determine a context
model, based on at least one of a shape, direction, ratio of width
and height, or size of the coding unit. Also, the image encoding
apparatus 200 generates a bitstream including information about a
split shape mode for splitting the coding unit based on the context
model.
[0220] The image encoding apparatus 200 may obtain an array for
mapping an index for the context model with at least one of the
shape, direction, ratio of width and height, or size of the coding
unit, in order to determine the context model. The image encoding
apparatus 200 may obtain, from the array, the index for the context
model, based on at least one of the shape, direction, ratio of
width and height, or size of the coding unit. The image encoding
apparatus 200 may determine the context model, based on the index
for the context model.
[0221] The image encoding apparatus 200 may determine the context
model, further based on block shape information including at least
one of a shape, direction, ratio of width and height, or size of a
neighboring coding unit adjacent to the coding unit, in order to
determine the context model. The neighboring coding unit may
include at least one of a coding unit located at bottom left, left,
top left, top, right, top right, or bottom right of the coding
unit.
[0222] Also, the image encoding apparatus 200 may compare the
length of width of the top neighboring coding unit with the length
of width of the coding unit to determine the context model. Also,
the image encoding apparatus 200 may compare the lengths of heights
of the left and right neighboring coding units with the length of
height of the coding unit. Also, the image encoding apparatus 200
may determine the context model, based on comparison results.
[0223] Because operations of the image encoding apparatus 200
include similar contents to operations of the image decoding
apparatus 100 described above with reference to FIGS. 3 through 20,
detailed descriptions thereof will be omitted.
[0224] Hereinafter, an image decoding apparatus 2100 and an image
encoding apparatus 2800 according to an embodiment will be
described with reference to FIGS. 21 through 32.
[0225] FIG. 21 is a block diagram of the image decoding apparatus
2100 according to an embodiment.
[0226] Referring to FIG. 21, the image decoding apparatus 2100
according to an embodiment may include an obtainer 2110 and a
prediction decoder 2130.
[0227] The image decoding apparatus 2100 according to an embodiment
may include a central processor (not shown) for controlling the
obtainer 2110 and the prediction decoder 2130. Alternatively, the
obtainer 2110 and the prediction decoder 2130 may operate
respectively by their own processors (not shown), and the
processors may operate mutually organically such that the image
decoding apparatus 2100 operates as a whole. Alternatively, the
obtainer 2110 and the prediction decoder 2130 may be controlled
under control of an external processor (not shown) of the image
decoding apparatus 2100.
[0228] The image decoding apparatus 2100 may include at least one
data storage (not shown) storing input and output data of the
obtainer 2110 and prediction decoder 2130. The image decoding
apparatus 2100 may include a memory controller (not shown) for
controlling data input and output of the at least one data
storage.
[0229] The image decoding apparatus 2100 may perform an image
decoding operation including prediction by connectively operating
with an internal video decoding processor or an external video
decoding processor so as to reconstruct an image via image
decoding. The internal video decoding processor of the image
decoding apparatus 2100 according an embodiment may perform a basic
image decoding operation as a separate processor, or as a central
processing unit or a graphics processing unit including an image
decoding processing module.
[0230] The image decoding apparatus 2100 may be included in the
image decoding apparatus 100 described above. For example, the
obtainer 2110 may be included in the bitstream obtainer 110 of the
image decoding apparatus 100 of FIG. 1, and the prediction decoder
2130 may be included in the decoder 120 of the image decoding
apparatus 100.
[0231] The image decoding apparatus 2100 may determine a motion
vector for reconstructing a current block encoded via inter
prediction.
[0232] A block may have a square shape, a rectangular shape, or any
geometric shape. A block according to an embodiment is not limited
to a data unit of a certain size, and may include a largest coding
unit, a coding unit, a prediction unit, a transformation unit, and
the like from among coding units based on a tree structure.
[0233] The obtainer 2110 obtains a bitstream including information
for decoding an image. The bitstream may include information about
at least one of a differential motion vector, a prediction motion
vector, a prediction direction (either uni-direction prediction or
bi-direction prediction), a reference image, and an MVR, according
to a prediction mode of the current block.
[0234] The prediction decoder 2130 obtains the motion vector of the
current block, based on the information included in the
bitstream.
[0235] The prediction decoder 2130 may determine whether adaptive
encoding has been applied to the differential motion vector of the
current block. The adaptive encoding with respect to the
differential motion vector may refer to an encoding method that is
used to represent the differential motion vector with a small
number of bits.
[0236] The prediction decoder 2130 may determine whether adaptive
encoding has been applied to the differential motion vector, based
on information indicating whether adaptive encoding has been
applied, the information included in the bitstream. The information
indicating whether adaptive encoding has been applied may include,
for example, an index or flag, but embodiments are not limited
thereto.
[0237] When adaptive encoding has been applied to the differential
motion vector, the prediction decoder 2130 determines a coding
factor value of the differential motion vector. The coding factor
value (or a factor value) is used in adaptive encoding of the
differential motion vector. Thus, according to an embodiment, the
coding factor value may include an integer equal to or greater than
1.
[0238] The prediction decoder 2130 may determine the coding factor
value, based on indication information of a coding factor value
included in the bitstream. The indication information of the coding
factor value may include a flag or index. When the indication
information of the coding factor value is an index, a coding factor
value for each index is illustrate in FIG. 22. In FIG. 22, when a
factor value indicating index is 0, the coding factor value may be
determined to be 1, and, when the factor value indicating index is
1, the coding factor value may be determined to be 4.
[0239] According to an embodiment, the prediction decoder 2130 may
determine the coding factor value, based on information related to
at least one of a current block, a pre-decoded block, a current
slice including the current block, a pre-decoded slice, a current
picture including the current block, and a pre-decoded picture. In
this case, information related to the coding factor value may not
be included in the bitstream. For example, the prediction decoder
2130 may determine a coding factor value for the differential
motion vector of the current block, based on at least one of the
size of the current block, the prediction mode of the current
block, the size of the pre-decoded block, the prediction mode of
the pre-decoded block, the coding factor value of the pre-decoded
block, the type of current slice, the type of pre-decoded slice,
the type of current picture, and the type of pre-decoded
picture.
[0240] As will be described later, the coding factor value may be
determined based on a first MVR of a first component of the motion
vector of the current block and a second MVR of a second component
of the motion vector of the current block.
[0241] The prediction decoder 2130 may determine a first result
value generated by applying adaptive encoding to the differential
motion vector, based on the information included in the bitstream.
As will be described later, the first result value may refer to a
value obtained by the image encoding apparatus 2800 applying
adaptive encoding to the differential motion vector of the current
block. The first result value may be smaller than the differential
motion vector of the current block. The prediction decoder 2130 may
obtain, for example, information indicating the sign of the first
result value and information indicating whether the absolute value
of the first result value is greater than 0, from the bitstream,
and may determine the first result value, based on the obtained
information.
[0242] The prediction decoder 2130 may obtain the differential
motion vector of the current block by applying the coding factor
value to the first result value according to a certain operation.
According to an embodiment, the certain operation may include a
multiplication operation. Alternatively, according to an
embodiment, the certain operation may include a linear operation
including at least one of multiplication and addition.
Alternatively, according to an embodiment, the certain operation
may include an exponentiation operation.
[0243] For example, when the coding factor value is 4, the first
result value is 2, and the certain operation is a multiplication
operation, the prediction decoder 2130 may determine the
differential motion vector of the current block to be 8(2*4). As
another example, when the coding factor value is 4, the first
result value is 2, and the certain operation is a exponentiation
operation, the prediction decoder 2130 may determine the
differential motion vector of the current block to be
16(2.sup.4).
[0244] According to an embodiment, the prediction decoder 2130 may
determine a second result value generated by applying adaptive
encoding to the differential motion vector, based on the
information included in the bitstream. As will be described later,
the second result value may refer to a value obtained by the image
encoding apparatus 2800 applying adaptive encoding to the
differential motion vector of the current block.
[0245] According to an embodiment, information of the number of
bits for representing the second result value may be included in
the bitstream. The obtainer 2110 may obtain bits corresponding to
the second result value, according to the information of the number
of bits, and the prediction decoder 2130 may determine the second
result value, based on the obtained bits. The number of bits for
representing the second result value may be less than that of bits
for representing the coding factor value. For example, when the
coding factor value is 8, four bits are needed to express the
coding factor value, but less than four bits may be needed to
express the second result value. This is because, when the certain
operation is a division operation, the second result value
corresponds to a value less than the coding factor value.
[0246] According to an embodiment, the information of the number of
bits for representing the second result value may be previously
determined in correspondence with the coding factor value, instead
of not being included in the bitstream. For example, when the
coding factor value is 8, the number of bits for representing the
second result value may be previously determined to be 3, and, when
the coding factor value is 7, the number of bits for representing
the second result value may be previously determined to be 2.
[0247] The prediction decoder 2130 may determine the differential
motion vector of the current block by applying the first result
value, the second result value, and the coding factor value to the
certain operation. For example, the certain operation may include
an operation of multiplying the first result value by the coding
factor value and adding the second result value to a result of the
multiplication (i.e., coding factor value* first result
value+second result value). In this case, the first result value
may be referred to as a quotient of the differential motion vector,
and the second result value may be referred to as a remainder of
the differential motion vector. For example, the certain operation
may include an operation of exponentiating the first result value
according to the coding factor value and adding the second result
value to a result of the exponentiation.
[0248] According to an embodiment, the prediction decoder 2130 may
determine the coding factor value and the first result value (and
the second result value) for each prediction direction of the
current block and each component of the differential motion vector.
In addition, the prediction decoder 2130 may determine the
differential motion vector for each prediction direction of the
current block and each component of the differential motion vector,
by using the coding factor value and the first result value.
[0249] FIG. 23 is a view for explaining a motion vector, a
prediction motion vector, and a differential motion vector when a
current block is predicted bidiectionally.
[0250] A current block 2310 may be unidirectionally predicted using
a reference picture 2330 included in list 0 or a reference picture
2350 included in list 1, or may be bidirectionally predicted using
the two reference pictures 2330 and 2350 included in list 0 and
list 1.
[0251] Referring to FIG. 23, the current block 2310 may be
bidirectionally predicted through the reference picture 2330
included in list 0 and the reference picture 2350 included in list
1, and, in this case, a differential motion vector 0 corresponding
to list 0 and a differential motion vector MVD1 corresponding to
list 1 may be determined. Each of the differential motion vectors
MVD0 and MVD1 may include a first component (e.g., a width
direction component of a block) value and a second component (e.g.,
a height direction component of a block) value. In this case, the
prediction decoder 2130 may determine a coding factor value and a
first result value for a first component value MVD0_X of the
differential motion vector MVD0 corresponding to list 0 to
determine the first component value MVD0_X of the differential
motion vector MVD0, and may determine a coding factor value and a
first result value for a second component value MVD0_Y of the
differential motion vector MVD0 corresponding to list 0 to
determine the second component value MVD0_Y of the differential
motion vector MVD0. The prediction decoder 2130 may determine a
coding factor value and a first result value for a first component
value MVD1_X of the differential motion vector MVD1 corresponding
to list 1 to determine the first component value MVD1_X of the
differential motion vector MVD1, and may determine a coding factor
value and a first result value for a second component value MVD1_Y
of the differential motion vector MVD1 corresponding to list 1 to
determine the second component value MVD1_Y of the differential
motion vector MVD1.
[0252] When the current block is unidirectionally predicted, the
prediction decoder 2130 may determine a coding factor value and a
first result value for a first component value of a differential
motion vector corresponding to list 0 or list 1 to determine the
first component value of the differential motion vector, and may
determine a coding factor value and a first result value for a
second component value of the differential motion vector
corresponding to list 0 or list 1 to determine the second component
value of the differential motion vector.
[0253] According to an embodiment, the prediction decoder 2130 may
determine only one coding factor value, and may determine the
differential motion vector by using a value derived by applying the
one coding factor value to the certain operation for each
prediction direction of the current block and/or each component
thereof.
[0254] According to an embodiment, when adaptive encoding is not
applied to the differential motion vector of the current block, the
prediction decoder 2130 may obtain the differential motion vector,
based on the information obtained from the bitstream, without
performing the above-described process of determining the coding
factor value, the above-described process of determining the first
result value, and the above-described process of applying the
coding factor value and the first result value to the certain
operation. The information included in the bitstream may include,
but is not limited to, information representing the sign of the
differential motion vector and information representing whether the
absolute value of the differential motion vector is greater than
0.
[0255] The prediction decoder 2130 may obtain the motion vector of
the current block, based on the differential motion vector of the
current block and the prediction motion vector of the current
block. According to an embodiment, the prediction motion vector of
the current block may be determined based on the motion vector of a
neighboring block temporally and/or spatially adjacent to the
current block.
[0256] FIG. 24 is a diagram illustrating a temporal and/or spatial
neighboring block temporally and/or spatially related to a current
block 2400. Referring to FIG. 24, the temporal neighboring block
may include at least one of a block F located at the same point as
the current block 2400 in a reference image having a different
picture order count (POC) from that of the current block 2400, and
a block G spatially adjacent to the block F. The spatial
neighboring block spatially related to the current block 2400 may
include a lower left outer block A, a lower left block B, an upper
right outer block C, an upper right block D, and an upper left
outer block E. Locations of neighboring blocks shown in FIG. 24 are
only examples, and locations of temporal neighboring blocks and
spatial neighboring blocks may vary according to an embodiment.
[0257] The prediction decoder 2130 may determine a median value of
the motion vector of at least one neighboring block to be the
prediction motion vector of the current block, or may configure a
prediction motion vector candidate by using the motion vectors of
the neighboring blocks and then determine one prediction motion
vector candidate to be the prediction motion vector of the current
block, based on the information included in the bitstream.
[0258] According to an embodiment, when the motion vector of the
current block is determined according to a certain MVR, the
prediction decoder 2130 may determine the motion vector of a
neighboring block pre-determined to correspond to the certain MVR
to be the prediction motion vector.
[0259] The prediction decoder 2130 may adjust the prediction motion
vector, based on the MVR of the current block, and may determine
the motion vector of the current block by using the adjusted
prediction motion vector and the differential motion vector.
[0260] The prediction decoder 2130 may store at least one candidate
MVR that may be the MVR of the motion vector of each block.
According to an embodiment, the at least one candidate MVR may
include at least one of a 1/8 pixel unit MVR, a 1/4 pixel unit MVR,
a 1/2 pixel unit MVR, a 1 pixel unit MVR, a 2 pixel unit MVR, a 4
pixel unit MVR, and an 8 pixel unit MVR. However, the candidate MVR
is not limited to the above example, and various values of pixel
unit MVRs may be included in the candidate MVR.
[0261] The prediction decoder 2130 may refer to information
representing the MVR included in the bitstream, in order to
determine the MVR of the motion vector of the current block.
According to an embodiment, the MVR of the motion vector of the
current block may be separately determined according to the
component of the motion vector of the current block. In detail, the
first MVR of the first component (e.g., the width direction
component of a block) of the motion vector of the current block and
the second MVR of the second component (e.g., the width direction
component of a block) of the motion vector of the current block may
be independently determined.
[0262] The bitstream may include information representing the first
MVR and the second MVR, and the information may include, for
example, an index or a flag. The prediction decoder 2130 may
previously store information of correspondence between information
representing an MVR and the MVR. Referring to FIG. 25, when the
first MVR and the second MVR are expressed as indexes within the
bitstream, an index 0 may represent a 1/8 pixel unit, and an index
1 may represent a 1/4 pixel unit.
[0263] According to an embodiment, the obtainer 2110 may obtain
information about the first MVR and information about the second
MVR for each inter-predicted coding unit.
[0264] FIG. 26 illustrates a syntax that obtains the information
about the first MVR and the information about the second MVR from
the bitstream.
[0265] Referring to FIG. 26, when a slice including a current
coding unit in a phrase a is not an I-slice, cu_skip_flag is
extracted in a phrase b. cu_skip_flag represents whether to apply a
skip mode to the current coding unit. When it is checked that the
skip mode is applied in a phrase c, the current coding unit is
processed according to the skip mode. When it is checked that the
skip mode is not applied in a phrase d, pred_mode_flag is extracted
in a phrase e. pred_mode_flag represents whether the current coding
unit has been intra-predicted or inter-predicted. When the current
coding unit has not been intra-predicted, namely, has been
inter-predicted, in a phrase f, pred_mvr_idx is extracted in a
phrase g. pred_mvr_idx is an index representing the MVR of the
current coding unit, and an MVR corresponding to each index may be
equal to Table 1 below.
TABLE-US-00001 TABLE 1 MVR Index 0 1 2 3 4 Resolution (R) in pel
1/4 1/2 1 2 4
[0266] FIG. 26 shows that one index pred_mvr_idx is obtained in the
phrase g, but the index pred_mvr_idx may be obtained for each
component of the motion vector of the current coding unit.
[0267] According to an embodiment, the prediction decoder 2130 may
directly determine the first MVR and the second MVR, based on
information related to at least one of a current block, a
pre-decoded block, a current slice including the current block, a
pre-decoded slice, a current picture including the current block,
and a pre-decoded picture. In this case, information representing
the first MVR and information representing the second MVR may not
be included in the bitstream.
[0268] For example, the prediction decoder 2130 may determine the
first MVR and the second MVR in consideration of the width and
height of the current block. When the width of the current block is
larger than the height thereof, the prediction decoder 2130 may
determine the first MVR to be greater than the second MVR. On the
other hand, when the height of the current block is greater than
the width thereof, the prediction decoder 2130 may determine the
second MVR to be greater than the first MVR. Alternatively, when
the width of the current block is larger than the height thereof,
the prediction decoder 2130 may determine the first MVR to be
smaller than the second MVR. On the other hand, when the height of
the current block is greater than the width thereof, the prediction
decoder 2130 may determine the second MVR to be smaller than the
first MVR.
[0269] According to an embodiment, the prediction decoder 2130 may
determine the first MVR and the second MVR according to the size of
the current block. For example, when the size of the current block
is equal to or greater than a certain size, the prediction decoder
2130 may determine the first MVR and the second MVR to be equal to
or greater than a 1 pixel unit, and, when the size of the current
block is less than the certain size, the prediction decoder 2130
may determine the first MVR and the second MVR to be less than a 1
pixel unit.
[0270] According to an embodiment, the prediction decoder 2130 may
determine the first MVR and the second MVR of the current block,
based on the first MVR and the second MVR of a pre-decoded block.
For example, when the first MVR of the pre-decoded block is a 1/4
pixel unit, the prediction decoder 2130 may determine the first MVR
of the current block to be also a 1/4 pixel unit, and, when the
second MVR of the pre-decoded block is a 1 pixel unit, the
prediction decoder 2130 may determine the second MVR of the current
block to be also a 1 pixel unit.
[0271] One MVR being greater than another MVR may mean that the
pixel unit of the one MVR is greater than that of the other MVR.
For example, the MVR of a 1 pixel unit is greater than the MVR of a
1/2 pixel unit, and the MVR of the 1/2 pixel unit is greater than
the MVR of a 1/4 pixel unit. In fact, more precise prediction is
possible when a motion vector is determined using the MVR of the
1/4 pixel unit, than when the motion vector is determined using the
MVR of the 1 pixel unit. However, for convenience of explanation, a
size difference of each MVR based on the size of a pixel unit is
described here.
[0272] The prediction decoder 2130 may determine a coding factor
value for adaptive encoding of the differential motion vector,
based on the first MVR and the second MVR. For example, the
prediction decoder 2130 may determine an average value of the first
MVR and the second MVR to be the coding factor value.
Alternatively, the prediction decoder 2130 may determine the coding
factor value by applying the first MVR and the second MVR to a
certain operation.
[0273] According to an embodiment, the prediction decoder 2130 may
adjust the prediction motion vector of the current block, based on
a difference between the first MVR and the second MVR of the
current block and a minimum MVR from among the at least one
candidate MVR. The prediction decoder 2130 may determine the motion
vector of the current block by using the prediction motion vector
selectively adjusted according to a result of the comparison
between the MVR sizes and the differential motion vector.
[0274] A process of adjusting the motion vector of a neighboring
block will be described later with reference to FIGS. 31 and
32.
[0275] The prediction decoder 2130 may search for a prediction
block from a reference image by using the motion vector of the
current block, and may reconstruct the current block by adding
dequantized and inversely-transformed residual data to the found
prediction block.
[0276] FIG. 27 is a flowchart of a method of decoding motion
information, according to an embodiment.
[0277] In operation S2710, when the image decoding apparatus 2100
determines that adaptive encoding has been applied to the
differential motion vector of the current block, the image decoding
apparatus 2100 determines the coding factor value.
[0278] As described above, the image decoding apparatus 2100 may
determine the coding factor value, based on the bitstream, or may
determine the coding factor value, based on information related to
at least one of a current block, a pre-decoded block, a current
slice including the current block, a pre-decoded slice, a current
picture including the current block, and a pre-decoded picture.
[0279] In operation S2720, the image decoding apparatus 2100
obtains a first result value by applying adaptive encoding to the
differential motion vector of the current block.
[0280] The image decoding apparatus 2100 may obtain the first
result value, based on information included in the bitstream.
[0281] According to an embodiment, the image decoding apparatus
2100 may obtain a second result value by applying adaptive encoding
to the differential motion vector of the current block. The image
decoding apparatus 2100 may obtain the second result value, based
on information included in the bitstream.
[0282] In operation S2730, the image decoding apparatus 2100
obtains the differential motion vector of the current block by
applying the coding factor value to the first result value
according to a certain operation. When the second result value is
obtained, the image decoding apparatus 2100 may obtain the
differential motion vector of the current block by applying the
coding factor value to the first result value and the second result
value according to a certain operation.
[0283] The certain operation may include multiplication,
exponentiation, and the like. The certain operation may also
include a linear operation including at least one of multiplication
and addition.
[0284] In operation S2740, the image decoding apparatus 2100
obtains a motion vector of the current block by using the
differential motion vector of the current block and the prediction
motion vector of the current block. The image decoding apparatus
2100 may obtain the motion vector of the current block in addition
to the differential motion vector of the current block and the
prediction motion vector of the current block.
[0285] The image decoding apparatus 2100 may adjust the prediction
motion vector of the current block, based on the MVR of the motion
vector of the current block, and, in this case, may obtain the
motion vector of the current block by using the adjusted prediction
motion vector and the differential motion vector.
[0286] The image decoding apparatus 2100 may determine the MVR of
the motion vector of the current block for each component of the
motion vector. For example, the image decoding apparatus 2100 may
determine the first MVR of the first component of the motion vector
of the current block and the second MVR of the second component of
the motion vector of the current block.
[0287] FIG. 28 is a block diagram of the image encoding apparatus
2800 according to an embodiment.
[0288] Referring to FIG. 28, the image encoding apparatus 2800
according to an embodiment may include a prediction encoder 2810
and a generator 2830.
[0289] The image encoding apparatus 2800 according to an embodiment
may include a central processor (not shown) for controlling the
prediction encoder 2810 and the generator 2830. Alternatively, the
prediction encoder 2810 and the generator 2830 may operate
respectively by their own processors (not shown), and the
processors may operate mutually organically such that the image
encoding apparatus 2800 operates as a whole. Alternatively, the
prediction encoder 2810 and the generator 2830 may be controlled
under control of an external processor (not shown) of the image
encoding apparatus 2800.
[0290] The image encoding apparatus 2800 may include at least one
data storage (not shown) where input and output data of the
prediction encoder 2810 and the generator 2830 is stored. The image
encoding apparatus 2800 may include a memory controller (not shown)
for controlling data input and output of the data storage.
[0291] The image encoding apparatus 2800 may perform an image
encoding operation including prediction by connectively operating
with an internal video encoding processor or an external video
encoding processor so as to encode an image. The internal video
encoding processor of the image encoding apparatus 2800 according
an embodiment may perform a basic image encoding operation, as a
separate processor, or as a central processing unit or a graphics
processing unit including an image encoding processing module.
[0292] The image encoding apparatus 2800 may be included in the
image encoding apparatus 200 described above. For example, the
generator 2830 may be included in the bitstream generator 210 of
the image encoding apparatus 200 of FIG. 2, and the prediction
encoder 2810 may be included in the encoder 220 of the image
encoding apparatus 200.
[0293] The image encoding apparatus 2800 may determine the motion
vector of the current block through inter prediction with respect
to the current block. The image encoding apparatus 2800 may encode
the differential motion vector determined using the motion vector
of the current block and the prediction motion vector of the
current block.
[0294] According to an embodiment, the prediction motion vector of
the current block may be determined based on the motion vector of a
neighboring block temporally and/or spatially adjacent to the
current block. The neighboring block temporally and/or spatially
adjacent to the current block is illustrated in FIG. 24.
[0295] The prediction encoder 2810 may determine a median value of
the motion vector of at least one neighboring block to be the
prediction motion vector of the current block, or may configure
prediction motion vector candidates by using the motion vectors of
the neighboring blocks and then determine one from the prediction
motion vector candidates to be the prediction motion vector of the
current block.
[0296] According to an embodiment, when the motion vector of the
current block is determined according to a certain MVR, the
prediction encoder 2810 may adjust the prediction motion vector and
may determine the differential motion vector of the current block
by using the adjusted prediction motion vector and the motion
vector of the current block. As described above, the prediction
encoder 2810 may determine the MVR of the motion vector of the
current block for each component of the motion vector. In other
words, the prediction encoder 2810 may determine the first MVR of
the first component of the motion vector of the current block and
the second MVR of the second component of the motion vector of the
current block. The first MVR and the second MVR may be the same as
each other or may be different from each other.
[0297] The prediction encoder 2810 may determine whether to apply
adaptive encoding to the differential motion vector of the current
block. For example, the prediction encoder 2810 may determine
whether to apply adaptive encoding, by comparing a bitrate of a
case where adaptive encoding is applied to the differential motion
vector of the current block with a bitrate of a case where adaptive
encoding is not applied to the differential motion vector of the
current block.
[0298] According to an embodiment, the prediction encoder 2810 may
determine whether to apply adaptive encoding, in consideration of
information related to at least one of a current block, a
pre-encoded block, a current slice including the current block, a
pre-encoded slice, a current picture including the current block,
and a pre-encoded picture.
[0299] When it is determined that adaptive encoding is applied to
the differential motion vector, the prediction encoder 2810
determines a coding factor value for adaptive encoding. The coding
factor value may include an integer that is equal to or greater
than 1.
[0300] The prediction encoder 2810 may determine a factor value
candidate causing a smallest overall number of bits of a first
result value and a second result value of the differential motion
vector and factor value indication information representing a
factor value candidate, the first result, the second result, and
the factor value indication information being derived by applying
each of a plurality of factor value candidates to the differential
motion vector of the current block, to be the coding factor value
of the differential motion vector of the current block. The
plurality of factor value candidates may include 1, 4, 8, 16, 32,
and the like.
[0301] The first result value and the second result value refer to
values derived by applying a coding factor value to the
differential motion vector according to a certain operation. The
first result value and the second result value may be smaller than
the differential motion vector of the current block. The certain
operation may include a division operation or a log operation.
Alternatively, the certain operation may include a linear operation
including at least one of division, addition, and subtraction.
[0302] For example, when the certain operation is division, the
differential motion vector is 32, and the coding factor value is 2,
the first result value may be 16(32/2). As another example, when
the certain operation is division, the differential motion vector
is 33, and the coding factor value is 2, the first result value may
be 16 and the second result value may be 1. The first result value
may be referred to as a quotient, and the second result value may
be referred to as a remainder.
[0303] For example, when the certain operation is a log operation,
the differential motion vector is 32, and the coding factor value
is 2, the first result value may be 5(log.sub.2 32). As another
example, when the certain operation is a log operation, the
differential motion vector is 33, and the coding factor value is 2,
the first result value may be 5(log.sub.2(33-1)) and the second
result value may be 1(33-32). In this case, the image decoding
apparatus 2100 may derive 32 by using a coding factor value of 2
and a first result value of 5 and add a second result value of 1 to
32 to determine a differential motion vector of 33.
[0304] The prediction encoder 2810 may determine one factor value
candidate to be the coding factor value of the current block, in
consideration of the number of bits necessary for representing the
first result value, the second result value, and indication
information of the above-described coding factor value, wherein the
first result value, the second result value, and the indication
information of the above-described coding factor value are derived
by applying each of a plurality of factor value candidates to the
differential motion vector of the current block according to a
certain operation.
[0305] According to an embodiment, the prediction encoder 2810 may
determine the coding factor value of the current block in
consideration of information related to at least one of a current
block, a pre-encoded block, a current slice including the current
block, a pre-encoded slice, a current picture including the current
block, and a pre-encoded picture. In this case, the prediction
encoder 2810 may determine the coding factor value according to the
same method as a method, performed by the above-described
prediction decoder 2130, of directly determining the coding factor
value of the current block.
[0306] According to an embodiment, the prediction decoder 2810 may
determine the coding factor value, based on the first MVR and the
second MVR of the motion vector of the current block.
[0307] According to an embodiment, the prediction encoder 2810 may
determine the coding factor value and the first result value (and
the second result value) for each prediction direction of the
current block and each component of the differential motion
vector.
[0308] According to an embodiment, when the prediction encoder 2810
determines that adaptive encoding is not applied to the
differential motion vector of the current block, the prediction
encoder 2810 may not perform the above-described process of
determining the coding factor value and the above-described process
of determining the first result value. Instead, the prediction
encoder 2810 may generate information about the differential motion
vector, for example, information representing the sign of the
differential motion vector and information representing whether the
absolute value of the differential motion vector is greater than 0
and so on, and may include the generated information in the
bitstream through the generator 2830 which will be described
later.
[0309] When determining the motion vector of the current block, the
prediction encoder 2810 may determine the first MVR of the first
component of the motion vector and the second MVR of the first
component of the motion vector, and may determine the first
component value and the second component value of the motion vector
according to the determined first MVR and the determined second
MVR.
[0310] The prediction encoder 2810 may store at least one candidate
MVR that may be the MVR of the motion vector of each block.
According to an embodiment, the at least one candidate MVR may
include at least one of a 1/8 pixel unit MVR, a 1/4 pixel unit MVR,
a 1/2 pixel unit MVR, a 1 pixel unit MVR, a 2 pixel unit MVR, a 4
pixel unit MVR, and an 8 pixel unit MVR. However, the candidate MVR
is not limited to the above example, and various values of pixel
unit MVRs may be included in the candidate MVR.
[0311] The prediction encoder 2810 may determine the first MVR and
the second MVR by comparing a performance difference between cases
where the motion vector of the current block is encoded using at
least one candidate MVR. The prediction encoder 2810 may determine
the first MVR and the second MVR from among the at least one
candidate MVR, based on costs. A rate-distortion cost may be used
to calculate the costs.
[0312] According to an embodiment, the prediction encoder 2810 may
determine the first MVR and the second MVR, based on information
related to at least one of a current block, a pre-encoded block, a
current slice including the current block, a pre-encoded slice, a
current picture including the current block, and a pre-encoded
picture.
[0313] For example, the prediction encoder 2810 may determine the
first MVR and the second MVR in consideration of the width and
height of the current block. When the width of the current block is
larger than the height thereof, the prediction encoder 2810 may
determine the first MVR to be greater than the second MVR. On the
other hand, when the height of the current block is greater than
the width thereof, the prediction encoder 2810 may determine the
second MVR to be greater than the first MVR. Alternatively, when
the width of the current block is larger than the height thereof,
the prediction encoder 2810 may determine the first MVR to be
smaller than the second MVR. On the other hand, when the height of
the current block is greater than the width thereof, the prediction
encoder 2810 may determine the second MVR to be smaller than the
first MVR.
[0314] According to an embodiment, the prediction encoder 2810 may
determine the first MVR and the second MVR according to the size of
the current block. For example, when the size of the current block
is equal to or greater than a certain size, the prediction encoder
2810 may determine the first MVR and the second MVR to be equal to
or greater than a 1 pixel unit, and, when the size of the current
block is less than the certain size, the prediction encoder 2810
may determine the first MVR and the second MVR to be less than a 1
pixel unit.
[0315] According to an embodiment, the prediction encoder 2810 may
determine the first MVR and the second MVR of the current block,
based on the first MVR and the second MVR of a pre-encoded block.
For example, when the first MVR of the pre-encoded block is a 1/4
pixel unit, the prediction encoder 2810 may determine the first MVR
of the current block to be also a 1/4 pixel unit, and, when the
second MVR of the pre-encoded block is a 1 pixel unit, the
prediction encoder 2810 may determine the second MVR of the current
block to be also a 1 pixel unit.
[0316] According to an embodiment, the prediction encoder 2810 may
adjust the prediction motion vector of the current block, based on
a difference between the first MVR and the second MVR of the
current block and a minimum MVR from among the at least one
candidate MVR. The prediction encoder 2810 may obtain the
differential motion vector of the current block by using the
prediction motion vector selectively adjusted according to a result
of the comparison between the MVR sizes and the motion vector.
[0317] A process of adjusting the prediction motion vector will be
described later with reference to FIGS. 31 and 32.
[0318] The generator 2830 generates a bitstream including
information generated as a result of encoding an image. The
bitstream may include the prediction mode of the current block,
information representing whether adaptive encoding has been applied
to the differential motion vector, and information about at least
one of the coding factor value, the first result value, the second
result value, the first MVR, the second MVR, and the differential
motion vector.
[0319] According to an embodiment, the generator 2830 may generate
the bitstream by using an Exponential-Golomb Coding method for the
first result value and using a Fixed Coding method for the second
result value.
[0320] According to an embodiment, the generator 2830 may include
information of the number of bits for representing the second
result value, in the bitstream. The number of bits for representing
the second result value may be less than that of bits for
representing the coding factor value. For example, when the coding
factor value is 8, four bits are needed to express the coding
factor value, and, in this case, less than four bits may be needed
to express the second result value. This is because, when the
certain operation is a division operation, the second result value
corresponds to a value less than the coding factor value. The
generator 2830 may include information indicating that, when the
second result value corresponds to 6, the number of bits for
representing the second result value is 3, in the bitstream.
[0321] According to an embodiment, when information of the number
of bits for representing the second result value is previously
determined in correspondence with the coding factor value, the
generator 2830 may not include the information of the number of
bits for representing the second result value, in the bitstream.
When the coding factor value is determined, the image decoding
apparatus 2100 may ascertain the information of the number of bits
for representing the second result value, and thus may obtain a
certain number of bits from the bitstream and may determine the
second result value, based on the obtained bits.
[0322] FIG. 29 is a flowchart of a method of encoding motion
information, according to an embodiment.
[0323] In operation S2910, the image encoding apparatus 2800
obtains the differential motion vector of the current block. The
image encoding apparatus 2800 may obtain the differential motion
vector by using the motion vector of the current block and the
prediction motion vector of the current block.
[0324] According to an embodiment, the image encoding apparatus
2800 may determine the first MVR of the first component of the
motion vector of the current block and the second MVR of the first
component of the motion vector of the current block, and may
determine the first component value and the second component value
of the motion vector of the current block according to the
determined first MVR and the determined second MVR.
[0325] According to an embodiment, the image encoding apparatus
2800 may determine the prediction motion vector of the current
block, based on the motion vector of at least one neighboring
block. The image encoding apparatus 2800 may adjust the prediction
motion vector, based on a result of a comparison between the first
and second MVRs and the minimum MVR from among at least one
candidate MVR.
[0326] In operation S2920, when the image encoding apparatus 2800
determines that adaptive encoding is to be applied to the
differential motion vector of the current block, the image encoding
apparatus 2800 determines the coding factor value.
[0327] As described above, the image encoding apparatus 2800 may
determine one factor value candidate from several factor value
candidates to be the coding factor value of the current block.
According to an embodiment, the image encoding apparatus 2800 may
determine the coding factor value, based on information related to
at least one of a current block, a pre-encoded block, a current
slice including the current block, a pre-encoded slice, a current
picture including the current block, and a pre-encoded picture.
[0328] According to an embodiment, the image encoding apparatus
2800 may determine the coding factor value, based on the first MVR
and the second MVR.
[0329] In operation S2930, the image encoding apparatus 2800 may
obtain the first result value by applying the coding factor value
to the differential motion vector of the current block according to
a certain operation. The image encoding apparatus 2800 may further
obtain the second result value by applying the coding factor value
to the differential motion vector of the current block according to
a certain operation.
[0330] In operation S2940, the image encoding apparatus 2800
generates the bitstream, based on the first result value. When the
second result value is also obtained, the image encoding apparatus
2800 may generate the bitstream, based on the first result value
and the second result value.
[0331] According to an embodiment, the bitstream may include the
prediction mode of the current block, information representing
whether adaptive encoding has been applied to the differential
motion vector, and information about at least one of the coding
factor value, the first result value, the second result value, the
first MVR, the second MVR, and the differential motion vector.
[0332] According to an embodiment, when adaptive encoding is not
applied to the differential motion vector of the current block, the
bitstream may not include information about the coding factor
value, the first result value, and the second result value.
[0333] FIG. 30 illustrates positions of pixels that may be
indicated by motion vectors according to a 1/4 pixel unit MVR, a
1/2 pixel unit MVR, a 1 pixel unit MVR, and a 2 pixel unit MVR.
[0334] (a), (b), (c), and (d) of FIG. 30 respectively illustrate
coordinates (marked by black squares) of pixels that may be
indicated by motion vectors of the 1/4 pixel unit MVR, the 1/2
pixel unit MVR, the 1 pixel unit MVR, and the 2 pixel unit MVR
based on coordinates (0, 0).
[0335] When a minimum MVR is the 1/4 pixel unit MVR, the
coordinates of the pixel that may be indicated by the motion vector
of the 1/4 pixel unit MVR become (a/4, b/4) (where a and b are
integers), the coordinates of the pixel that may be indicated by
the motion vector of the 1/2 pixel unit MVR become (2c/4, 2d/4)
(where c and d are integers), the coordinates of the pixel that may
be indicated by the motion vector of the 1 pixel unit MVR become
(4e/4, 4f/4) (where e and f are integers), and the coordinates of
the pixel that may be indicated by the motion vector of the 2 pixel
unit MVR become (8g/4, 8h/4) (where g and h are integers). That is,
when a minimum MVR has a 2.sup.m (m is an integer) pixel unit,
coordinates of a pixel that may be indicated by a 2.sup.m (n is an
integer) pixel unit MVR become (2.sup.n-m*i/2.sup.-m,
2.sup.n-mj/2.sup.-m) (i and j are integers). Although a motion
vector is determined according to a specific MVR, the motion vector
is represented by coordinates in an image interpolated according to
a 1/4 pixel unit.
[0336] According to an embodiment, because a motion vector is
interpolated in an image interpolated according to a minimum MVR,
in order to represent the motion vector by using an integer, the
motion vector of an integer unit may be represented by multiplying
the motion vector by a reciprocal of a pixel unit value of the
minimum MVR, for example, 2.sup.-m when the minimum MVR has a
2.sup.m (m is an integer) pixel unit. The motion vector of the
integer unit multiplied by 2.sup.-m may be used in the image
decoding apparatus 2100 and the image encoding apparatus 2800.
[0337] When the motion vector of the 1/2 pixel unit MVR starting
from the coordinates (0, 0) indicates coordinates (2/4, 6/4) and
the minimum MVR has a 1/4 pixel unit, the image encoding apparatus
2800 may determine (2, 6), which is obtained by multiplying the
motion vector by an integer 4, as a motion vector.
[0338] When a size of an MVR is less than a 1 pixel unit, in order
to perform motion prediction in a subpixel unit, the image encoding
apparatus 2800 according to an embodiment may search for a block
similar to a current block in a reference image based on the
subpixel unit according to a motion vector determined in an integer
pixel unit.
[0339] For example, when an MVR of a current block is the 1/4 pixel
unit MVR, the image encoding apparatus 2800 may determine a motion
vector in an integer pixel unit, may interpolate a reference image
to generate subpixels of 1/2 pixel unit, and then may search for a
most similar prediction bock in a (-1 .about.1, -1 .about.1) range
based on the motion vector determined in the integer pixel unit.
Next, the image encoding apparatus 2800 may interpolate the
reference image to generate subpixels of 1/4 pixel unit again, and
then may search for a most similar prediction block in the (-1
.about.1, -1 .about.1) range based on a motion vector determined in
a 1/2 pixel unit, thereby determining a motion vector of the final
1/4 pixel unit MVR.
[0340] For example, when a motion vector of an integer pixel unit
is (-4, -3) based on the coordinates (0, 0), a motion vector in the
1/2 pixel unit MVR becomes (-8, -6) (=(-4*2, -3*2)); and when the
motion vector moves by (0, -1), the motion vector of the 1/2 pixel
unit MVR is finally determined to be (-8, -7) (=(-8, -6-1)). When a
motion vector in the 1/4 pixel unit MVR is changed to (-16, -14)
(=(-8*2, -7*2)); and when the motion vector moves by (-1, 0) again,
a final motion vector of the 1/4 pixel unit MVR may be determined
to be (-17, -14) (=(-16-1, -14)).
[0341] As described above, when the MVR of the motion vector of the
current block is determined for each component of the motion
vector, the image encoding apparatus 2800 may determine the first
component value of the motion vector of the current block according
to the first MVR and may determine the second component value of
the motion vector of the current block according to the second
MVR.
[0342] When the MVR of the current block is higher than the 1 pixel
unit MVR, in order to perform motion prediction in a large pixel
unit, the image encoding apparatus 2800 according to an embodiment
may search for a block similar to the current block in a reference
picture based on a pixel unit larger than a 1 pixel unit according
to a motion vector determined in an integer pixel unit. Pixels
located in pixel units (e.g., a 2 pixel unit, a 3 pixel unit, and a
4 pixel unit) larger than the 1 pixel unit may be referred to as
super pixels.
[0343] A prediction motion vector adjusting method selectively
performed by the image encoding apparatus 2800 and the image
decoding apparatus 2100 according to an embodiment will now be
described with reference to FIGS. 31 and 32.
[0344] When an MVR of the current block is higher than a minimum
MVR from among selectable candidate MVRs, the image encoding
apparatus 2800 and the image decoding apparatus 2100 may adjust a
prediction motion vector of the current block.
[0345] In order to adjust the prediction motion vector represented
by coordinates in an image interpolated according to the minimum
MVR to the MVR of the current block, the image encoding apparatus
2800 and the image decoding apparatus 2100 may adjust the
prediction motion vector to indicate neighboring pixels instead of
a pixel indicated by the prediction motion vector.
[0346] For example, when the minimum MVR is a 1/4 pixel unit and
the MVR of the current block is a 1 pixel unit, in order to adjust
a prediction motion vector A indicating a pixel 3110 of coordinates
(19, 27) based on coordinates (0, 0) in FIG. 31 to a 1 pixel unit
MVR that is the MVR of the current block, the coordinates (19, 27)
of the pixel 3110 indicated by the prediction motion vector A may
be divided by an integer 4 (that is, may be downscaled), and
coordinates (19/4, 27/4) obtained as a division result may not
indicate an integer pixel unit.
[0347] The image encoding apparatus 2800 and the image decoding
apparatus 2100 may adjust the downscaled prediction motion vector
to indicate an integer pixel unit. For example, coordinates of
neighboring integer pixels around the coordinates (19/4, 27/4) are
(16/4, 28/4), (16/4, 24/4), (20/4, 28/4), and (20/4, 24/4). In this
case, the image encoding apparatus 2800 and the image decoding
apparatus 2100 may adjust the downscaled prediction motion vector A
to indicate the coordinates (20/4, 28/4) located at the right-top
instead of the coordinates (19/4, 27/4), and then may multiply an
integer 4 (that is, upscale) again so that a finally adjusted
prediction motion vector D indicates a pixel 3140 corresponding to
coordinates (20, 28).
[0348] Referring to FIG. 31, the prediction motion vector A before
adjustment may indicate the pixel 3110, and the finally adjusted
prediction motion vector D may indicate the pixel 3140 of an
integer unit located at the right-top of the pixel 3110.
[0349] When adjusting a prediction motion vector according to an
MVR of a current block, the image encoding apparatus 2800 and the
image decoding apparatus 2100 according to an embodiment may cause
the adjusted prediction motion vector to indicate a pixel located
at the right-top of a pixel indicated by the prediction motion
vector before adjustment. The image encoding apparatus 2800 and the
image decoding apparatus 2100 according to another embodiment may
cause the adjusted prediction motion vector to indicate a pixel
located at the left-top, a pixel located at the left-bottom, or a
pixel located at the right-bottom of the pixel indicated by the
prediction motion vector before adjustment.
[0350] According to an embodiment, when any one of an x-coordinate
value and a y-coordinate value indicated by the downscaled
prediction motion vector indicates an integer pixel, the image
encoding apparatus 2800 and the image decoding apparatus 2100 may
increase or decrease only the coordinate value not indicating the
integer pixel to indicate an integer pixel. That is, when the
x-coordinate value indicated by the downscaled prediction motion
vector does not indicate an integer pixel, the image encoding
apparatus 2800 and the image decoding apparatus 2100 may cause the
x-coordinate value of the adjusted prediction motion vector to
indicate an integer pixel located at the left or the right of the
pixel indicated by the x-coordinate value of the prediction motion
vector before adjustment. Alternatively, when the y-coordinate
value indicated by the downscaled prediction motion vector does not
indicate an integer pixel, the image encoding apparatus 2800 and
the image decoding apparatus 2100 may cause the y-coordinate value
of the adjusted prediction motion vector to indicate an integer
pixel located at the top or the bottom of the pixel indicated by
the y-coordinate value of the prediction motion vector before
adjustment.
[0351] When adjusting the prediction motion vector, the image
encoding apparatus 2800 and the image decoding apparatus 2100 may
differently select a point indicated by the adjusted prediction
motion vector according to the MVR of the current block.
[0352] For example, referring to FIG. 32, when the MVR of the
current block is a 1/2 pixel unit MVR, the image encoding apparatus
2800 and the image decoding apparatus 2100 may cause the adjusted
prediction motion vector to indicate a pixel 3230 at the left-top
of a pixel 3210 indicated by the prediction motion vector before
adjustment; when the MVR of the current block is a 1 pixel unit
MVR, the image encoding apparatus 2800 and the image decoding
apparatus 2100 may cause the adjusted prediction motion vector to
indicate a pixel 3220 at the right-top of the pixel 3210 indicated
by the prediction motion vector before adjustment; and when the MVR
of the current block is a 2 pixel unit MVR, the image encoding
apparatus 2800 and the image decoding apparatus 2100 may cause the
adjusted prediction motion vector to indicate a pixel 3240 at the
right-bottom of the pixel 3210 indicated by the prediction motion
vector before adjustment.
[0353] The image encoding apparatus 2800 and the image decoding
apparatus 2100 may determine which pixel is to be indicated by the
adjusted prediction motion vector, based on at least one from among
the MVR of the current block, the prediction motion vector,
information of a neighboring block, encoding information, and an
arbitrary pattern.
[0354] When the prediction motion vector is adjusted in
consideration of the MVR of the current block and the minimum MVR,
the image encoding apparatus 2800 and the image decoding apparatus
2100 may adjust the prediction motion vector according to Equation
1.
pMV'=((pMV>>k)+offset).gtoreq..gtoreq.k [Equation 1]
[0355] In Equation 1, when pMV' denotes the adjusted prediction
motion vector, and k that is a value determined according to a
difference between the MVR of the current block and the minimum MVR
may be m-n when the MVR of the current block is a 2.sup.m pixel
unit (m is an integer), the minimum MVR is a 2.sup.n pixel unit (n
is an integer), and m>n.
[0356] According to an embodiment, k may be an index of an MVR, and
when candidate MVRs include a 1/4 pixel unit MVR, a 1/2 pixel unit
MVR, a 1 pixel unit MVR, a 2 pixel unit MVR, and a 4 pixel unit
MVR, MVRs corresponding to indices are as shown in Table 1. When an
MVR index is received from a bitstream, the image decoding
apparatus 2100 may adjust the motion vector of the candidate block
according to Equation 1 by using the MVR index as k.
[0357] Also, in Equation 1, >> or << that is a bit
shift operation refers to an operation of reducing or increasing a
size of the prediction motion vector. Also, offset refers to a
value added or subtracted to indicate an integer pixel when pMV
downscaled according to a k value does not indicate an integer
pixel. offset may be differently determined according to each of an
x-coordinate value and a y-coordinate value of a basic MV.
[0358] According to an embodiment, when the downscaled pMV is
changed to indicate an integer pixel, the image encoding apparatus
2800 and the image decoding apparatus 2100 may change the
downscaled pMV according to the same criterion.
[0359] According to an embodiment, when an x-coordinate value and a
y-coordinate value of the downscaled pMV do not indicate an integer
pixel, the image encoding apparatus 2800 and the image decoding
apparatus 2100 may always increase or decrease the x-coordinate
value and the y-coordinate value of the downscaled pMV to indicate
an integer pixel. Alternatively, the image encoding apparatus 2800
and the image decoding apparatus 2100 may round the x-coordinate
value and the y-coordinate value of the downscaled pMV to indicate
an integer pixel.
[0360] According to an embodiment, when the prediction motion
vector is adjusted, the image encoding apparatus 2800 and the image
decoding apparatus 2100 may omit downscaling and upscaling of the
prediction motion vector, and may adjust the prediction motion
vector in a coordinate plane in a reference image interpolated
according to the minimum MVR to indicate a pixel unit corresponding
to the MVR of the current block.
[0361] Also, according to an embodiment, when the prediction motion
vector is adjusted in consideration of the MVR of the current block
and the minimum MVR, the image encoding apparatus 2800 and the
image decoding apparatus 2100 may adjust the prediction motion
vector according to Equation 2, instead of Equation 1.
pMV'=((pMV+offset)>>k).gtoreq..gtoreq.k [Equation 2]
[0362] Although Equation 2 is similar to Equation 1, unlike in
Equation 1 where offset is applied to the downscaled pMV, offset is
applied to original pMV and then is downscaled according to k.
[0363] The image encoding apparatus 2800 may find a motion vector
of the current block by using the MVR of the current block, and may
obtain a difference between the motion vector of the current block
and the selectively adjusted prediction motion vector as a
differential motion vector. The image decoding apparatus 2100 may
obtain a sum of the differential motion vector of the current block
and the selectively adjusted prediction motion vector, as the
motion vector of the current block. According to an embodiment,
when the MVR of the current block is less than a 1 pixel unit MVR,
the image decoding apparatus 2100 may interpolate the reference
image according to the minimum MVR and then may search for a
prediction block according to the motion vector of the current
block. Also, when the MVR of the current block is equal to or
higher than a 1 pixel unit MVR, the image decoding apparatus 2100
may search for the prediction block according to the motion vector
of the current block without interpolating the reference image.
[0364] Adjustment of the prediction motion vector has been
described above as being performed according to a result of the
comparison between the MVR of the current block and the minimum
MVR. However, as described above, when the first MVR of the first
component of the motion vector of the current block and the second
MVR of the second component of the motion vector of the current
block are independently determined, the first component value and
the second component value of the prediction motion vector may also
be independently adjusted. In detail, when the first MVR is greater
than the minimum MVR, the image encoding apparatus 2800 and the
image decoding apparatus 2100 may adjust the first component value
of the prediction motion vector; and, when the second MVR is
greater than the minimum MVR, the image encoding apparatus 2800 and
the image decoding apparatus 2100 may adjust the second component
value of the prediction motion vector.
[0365] For example, it is assumed that the minimum MVR is a 1/4
pixel unit, the first MVR of the current block is a 1 pixel unit,
and the first component value of the prediction motion vector
indicates a coordinate (19) based on the coordinates (0,0). In
order to adjust the first component value of the prediction motion
vector to a 1 pixel unit MVR that is the MVR of the current block,
the coordinate (19) of a pixel indicated by the first component
value may be divided by 4, and coordinates (19/4) corresponding to
a result of the division may not indicate an integer pixel
unit.
[0366] The image encoding apparatus 2800 and the image decoding
apparatus 2100 may adjust a downscaled first component vector to
indicate an integer pixel unit. For example, respective coordinates
of neighboring integer pixels located in a first component
direction based on the coordinates (19/4) become (16/4) and (20/4).
In this case, the image encoding apparatus 2800 and the image
decoding apparatus 2100 may adjust the downscaled first component
value to indicate the coordinates (20/4) located at the right
instead of the coordinates (19/4), and then may multiply an integer
4 (that is, upscale) again so that a finally adjusted first
component value indicates a pixel corresponding to a coordinate
(20). According to an embodiment, the image encoding apparatus 2800
and the image decoding apparatus 2100 may adjust the downscaled
first component value to the coordinates (16/4) located at the left
instead of the coordinates (19/4).
[0367] For example, it is assumed that the minimum MVR is a 1/4
pixel unit, the second MVR of the current block is a 1 pixel unit,
and the second component value of the prediction motion vector
indicates a coordinate (27) based on the coordinates (0,0). In
order to adjust the second component value of the prediction motion
vector to a 1 pixel unit MVR that is the MVR of the current block,
the coordinate (27) of a pixel indicated by the second component
value may be divided by 4, and coordinates (27/4) corresponding to
a result of the division may not indicate an integer pixel
unit.
[0368] The image encoding apparatus 2800 and the image decoding
apparatus 2100 may adjust a downscaled second component vector to
indicate an integer pixel unit. For example, respective coordinates
of neighboring integer pixels located in a second component
direction based on the coordinates (27/4) become (24/4) and (28/4).
In this case, the image encoding apparatus 2800 and the image
decoding apparatus 2100 may adjust the downscaled second component
value to indicate the coordinates (28/4) located at the top instead
of the coordinates (27/4), and then may multiply an integer 4 (that
is, upscale) again so that a finally adjusted second component
value indicates a pixel corresponding to a coordinate (28).
According to an embodiment, the image encoding apparatus 2800 and
the image decoding apparatus 2100 may adjust the downscaled second
component value to the coordinates (24/4) located at the bottom
instead of the coordinates (27/4).
[0369] According to an embodiment, the image encoding apparatus
2800 and the image decoding apparatus 2100 may adjust the first
component value and the second component value of the prediction
motion vector, based on Equation 1 or 2.
[0370] Meanwhile, the embodiments of the disclosure described above
may be written as computer-executable programs that may be stored
in a medium.
[0371] The medium may continuously store the computer-executable
programs, or temporarily store the computer-executable programs or
instructions for execution or downloading. Also, the medium may be
any one of various recording media or storage media in which a
single piece or plurality of pieces of hardware are combined, and
the medium is not limited to a medium directly connected to a
computer system, but may be distributed on a network. Examples of
the medium include magnetic media, such as a hard disk, a floppy
disk, and a magnetic tape, optical recording media, such as CD-ROM
and DVD, magneto-optical media such as a floptical disk, and ROM,
RAM, and a flash memory, which are configured to store program
instructions. Other examples of the medium include recording media
and storage media managed by application stores distributing
applications or by websites, servers, and the like supplying or
distributing other various types of software.
[0372] While one or more embodiments of the disclosure have been
described with reference to the figures, it will be understood by
those of ordinary skill in the art that various changes in form and
details may be made therein without departing from the spirit and
scope as defined by the following claims.
* * * * *